21656664260 has 288 divisors, whose sum is σ = 59122224000. Its totient is φ = 6587965440.

The previous prime is 21656664257. The next prime is 21656664269. The reversal of 21656664260 is 6246665612.

It is a happy number.

It is a super-2 number, since 2×21656664260² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is not an unprimeable number, because it can be changed into a prime (21656664269) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 145346666 + ... + 145346814.

It is an arithmetic number, because the mean of its divisors is an integer number (205285500).

Almost surely, 2^21656664260 is an apocalyptic number.

21656664260 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 21656664260, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29561112000).

21656664260 is an abundant number, since it is smaller than the sum of its proper divisors (37465559740).

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

21656664260 is a wasteful number, since it uses less digits than its factorization.

21656664260 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 419 (or 410 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 44.

The spelling of 21656664260 in words is "twenty-one billion, six hundred fifty-six million, six hundred sixty-four thousand, two hundred sixty".