21655645525 has 6 divisors (see below), whose sum is σ = 26853000482. Its totient is φ = 17324516400.

The previous prime is 21655645499. The next prime is 21655645537. The reversal of 21655645525 is 52554655612.

It can be written as a sum of positive squares in 3 ways, for example, as 291145969 + 21364499556 = 17063^2 + 146166^2 .

It is not a de Polignac number, because 21655645525 - 2⁵ = 21655645493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 433112886 + ... + 433112935.

Almost surely, 2^21655645525 is an apocalyptic number.

21655645525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21655645525 is a deficient number, since it is larger than the sum of its proper divisors (5197354957).

21655645525 is an equidigital number, since it uses as much as digits as its factorization.

21655645525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 866225831 (or 866225826 counting only the distinct ones).

The product of its digits is 1800000, while the sum is 46.

The spelling of 21655645525 in words is "twenty-one billion, six hundred fifty-five million, six hundred forty-five thousand, five hundred twenty-five".