21078654660 has 144 divisors (see below), whose sum is σ = 74102176512. Its totient is φ = 4750099200.

The previous prime is 21078654629. The next prime is 21078654661. The reversal of 21078654660 is 6645687012.

21078654660 is a `hidden beast` number, since 2 + 107 + 86 + 5 + 466 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21078654661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 28351 + ... + 207270.

It is an arithmetic number, because the mean of its divisors is an integer number (514598448).

Almost surely, 2^21078654660 is an apocalyptic number.

21078654660 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 21078654660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37051088256).

21078654660 is an abundant number, since it is smaller than the sum of its proper divisors (53023521852).

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

21078654660 is a wasteful number, since it uses less digits than its factorization.

21078654660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 235714 (or 235709 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 21078654660 in words is "twenty-one billion, seventy-eight million, six hundred fifty-four thousand, six hundred sixty".