21655355620 has 12 divisors (see below), whose sum is σ = 45476246844. Its totient is φ = 8662142240.

The previous prime is 21655355581. The next prime is 21655355651. The reversal of 21655355620 is 2655355612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 3564567616 + 18090788004 = 59704^2 + 134502^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 541383871 + ... + 541383910.

It is an arithmetic number, because the mean of its divisors is an integer number (3789687237).

Almost surely, 2^21655355620 is an apocalyptic number.

21655355620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21655355620 is an abundant number, since it is smaller than the sum of its proper divisors (23820891224).

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

21655355620 is a wasteful number, since it uses less digits than its factorization.

21655355620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1082767790 (or 1082767788 counting only the distinct ones).

The product of its (nonzero) digits is 270000, while the sum is 40.

The spelling of 21655355620 in words is "twenty-one billion, six hundred fifty-five million, three hundred fifty-five thousand, six hundred twenty".