21550987656 has 192 divisors, whose sum is σ = 66585355200. Its totient is φ = 6529818240.

The previous prime is 21550987573. The next prime is 21550987673. The reversal of 21550987656 is 65678905512.

21550987656 is a `hidden beast` number, since 2 + 1 + 5 + 509 + 87 + 6 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2583300 + ... + 2591628.

It is an arithmetic number, because the mean of its divisors is an integer number (346798725).

Almost surely, 2^21550987656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21550987656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33292677600).

21550987656 is an abundant number, since it is smaller than the sum of its proper divisors (45034367544).

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

21550987656 is an equidigital number, since it uses as much as digits as its factorization.

21550987656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8383 (or 8345 counting only the distinct ones).

The product of its (nonzero) digits is 4536000, while the sum is 54.

The spelling of 21550987656 in words is "twenty-one billion, five hundred fifty million, nine hundred eighty-seven thousand, six hundred fifty-six".