21621621625 has 32 divisors (see below), whose sum is σ = 28163824416. Its totient is φ = 16556800000.

The previous prime is 21621621601. The next prime is 21621621667. The reversal of 21621621625 is 52612612612.

It can be written as a sum of positive squares in 16 ways, for example, as 21616938729 + 4682896 = 147027^2 + 2164^2 .

It is not a de Polignac number, because 21621621625 - 2⁹ = 21621621113 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 231825 + ... + 311425.

It is an arithmetic number, because the mean of its divisors is an integer number (880119513).

Almost surely, 2^21621621625 is an apocalyptic number.

21621621625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21621621625 is a deficient number, since it is larger than the sum of its proper divisors (6542202791).

21621621625 is an equidigital number, since it uses as much as digits as its factorization.

21621621625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79710 (or 79700 counting only the distinct ones).

The product of its digits is 17280, while the sum is 34.

The spelling of 21621621625 in words is "twenty-one billion, six hundred twenty-one million, six hundred twenty-one thousand, six hundred twenty-five".