21031556375 has 16 divisors (see below), whose sum is σ = 27791348832. Its totient is φ = 15835523200.

The previous prime is 21031556369. The next prime is 21031556389. The reversal of 21031556375 is 57365513012.

It is not a de Polignac number, because 21031556375 - 2¹⁶ = 21031490839 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 15 ways as a sum of consecutive naturals, for example, 4946477 + ... + 4950726.

It is an arithmetic number, because the mean of its divisors is an integer number (1736959302).

Almost surely, 2^21031556375 is an apocalyptic number.

21031556375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21031556375 is a deficient number, since it is larger than the sum of its proper divisors (6759792457).

21031556375 is an equidigital number, since it uses as much as digits as its factorization.

21031556375 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9897235 (or 9897225 counting only the distinct ones).

The product of its (nonzero) digits is 94500, while the sum is 38.

The spelling of 21031556375 in words is "twenty-one billion, thirty-one million, five hundred fifty-six thousand, three hundred seventy-five".