21661877180 has 48 divisors (see below), whose sum is σ = 47017227936. Its totient is φ = 8376825600.

The previous prime is 21661877117. The next prime is 21661877197. The reversal of 21661877180 is 8177816612.

It is a super-2 number, since 2×21661877180² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22955 + ... + 209405.

It is an arithmetic number, because the mean of its divisors is an integer number (979525582).

Almost surely, 2^21661877180 is an apocalyptic number.

21661877180 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 21661877180, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23508613968).

21661877180 is an abundant number, since it is smaller than the sum of its proper divisors (25355350756).

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

21661877180 is a wasteful number, since it uses less digits than its factorization.

21661877180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186654 (or 186652 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 47.

The spelling of 21661877180 in words is "twenty-one billion, six hundred sixty-one million, eight hundred seventy-seven thousand, one hundred eighty".