21655218072 has 16 divisors (see below), whose sum is σ = 54138045240. Its totient is φ = 7218406016.

The previous prime is 21655218071. The next prime is 21655218097. The reversal of 21655218072 is 27081255612.

It is a self number, because there is not a number n which added to its sum of digits gives 21655218072.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655218071) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 451150353 + ... + 451150400.

Almost surely, 2^21655218072 is an apocalyptic number.

It is an amenable number.

21655218072 is an abundant number, since it is smaller than the sum of its proper divisors (32482827168).

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

21655218072 is a wasteful number, since it uses less digits than its factorization.

21655218072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 902300762 (or 902300758 counting only the distinct ones).

The product of its (nonzero) digits is 67200, while the sum is 39.

The spelling of 21655218072 in words is "twenty-one billion, six hundred fifty-five million, two hundred eighteen thousand, seventy-two".