21980888398656 has 560 divisors, whose sum is σ = 71512614716928. Its totient is φ = 6620598374400.

The previous prime is 21980888398631. The next prime is 21980888398661. The reversal of 21980888398656 is 65689388808912.

21980888398656 is a `hidden beast` number, since 2 + 1 + 98 + 0 + 8 + 88 + 398 + 65 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (81).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 12983394546 + ... + 12983396238.

Almost surely, 2^{21980888398656} 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 21980888398656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35756307358464).

21980888398656 is an abundant number, since it is smaller than the sum of its proper divisors (49531726318272).

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

21980888398656 is a wasteful number, since it uses less digits than its factorization.

21980888398656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2972 (or 2953 counting only the distinct ones).

The product of its (nonzero) digits is 2866544640, while the sum is 81.

The spelling of 21980888398656 in words is "twenty-one trillion, nine hundred eighty billion, eight hundred eighty-eight million, three hundred ninety-eight thousand, six hundred fifty-six".