21621337721575 has 6 divisors (see below), whose sum is σ = 26810458774784. Its totient is φ = 17297070177240.

The previous prime is 21621337721549. The next prime is 21621337721623. The reversal of 21621337721575 is 57512773312612.

It is not a de Polignac number, because 21621337721575 - 2¹⁹ = 21621337197287 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 432426754407 + ... + 432426754456.

Almost surely, 2^{21621337721575} is an apocalyptic number.

21621337721575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21621337721575 is a deficient number, since it is larger than the sum of its proper divisors (5189121053209).

21621337721575 is an equidigital number, since it uses as much as digits as its factorization.

21621337721575 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 864853508873 (or 864853508868 counting only the distinct ones).

The product of its digits is 3704400, while the sum is 52.

The spelling of 21621337721575 in words is "twenty-one trillion, six hundred twenty-one billion, three hundred thirty-seven million, seven hundred twenty-one thousand, five hundred seventy-five".