21656021125 has 16 divisors (see below), whose sum is σ = 27039729600. Its totient is φ = 17316474000.

The previous prime is 21656021119. The next prime is 21656021143. The reversal of 21656021125 is 52112065612.

It is not a de Polignac number, because 21656021125 - 2¹³ = 21656012933 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 225726 + ... + 307024.

It is an arithmetic number, because the mean of its divisors is an integer number (1689983100).

Almost surely, 2^21656021125 is an apocalyptic number.

21656021125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21656021125 is a deficient number, since it is larger than the sum of its proper divisors (5383708475).

21656021125 is an equidigital number, since it uses as much as digits as its factorization.

21656021125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83445 (or 83435 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 31.

Adding to 21656021125 its reverse (52112065612), we get a palindrome (73768086737).

The spelling of 21656021125 in words is "twenty-one billion, six hundred fifty-six million, twenty-one thousand, one hundred twenty-five".