21891578428980 has 144 divisors (see below), whose sum is σ = 71535426724944. Its totient is φ = 5386967838720.

The previous prime is 21891578428969. The next prime is 21891578428981. The reversal of 21891578428980 is 8982487519812.

21891578428980 is a `hidden beast` number, since 2 + 1 + 8 + 9 + 1 + 578 + 42 + 8 + 9 + 8 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 13992656936976 + 7898921492004 = 3740676^2 + 2810502^2 .

It is a super-2 number, since 2×21891578428980² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21891578428899 and 21891578428908.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891578428981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 5804362 + ... + 8801918.

It is an arithmetic number, because the mean of its divisors is an integer number (496773796701).

Almost surely, 2^{21891578428980} is an apocalyptic number.

21891578428980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21891578428980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35767713362472).

21891578428980 is an abundant number, since it is smaller than the sum of its proper divisors (49643848295964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21891578428980 is a wasteful number, since it uses less digits than its factorization.

21891578428980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000706 (or 3000701 counting only the distinct ones).

The product of its (nonzero) digits is 185794560, while the sum is 72.

The spelling of 21891578428980 in words is "twenty-one trillion, eight hundred ninety-one billion, five hundred seventy-eight million, four hundred twenty-eight thousand, nine hundred eighty".