31511400021 has 6 divisors (see below), whose sum is σ = 45516466710. Its totient is φ = 21007600008.

The previous prime is 31511399981. The next prime is 31511400047. The reversal of 31511400021 is 12000411513.

It can be written as a sum of positive squares in only one way, i.e., 28210897521 + 3300502500 = 167961^2 + 57450^2 .

It is not a de Polignac number, because 31511400021 - 2⁶ = 31511399957 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31511399967 and 31511400003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31511400071) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1750633326 + ... + 1750633343.

It is an arithmetic number, because the mean of its divisors is an integer number (7586077785).

Almost surely, 2^31511400021 is an apocalyptic number.

It is an amenable number.

31511400021 is a deficient number, since it is larger than the sum of its proper divisors (14005066689).

31511400021 is a wasteful number, since it uses less digits than its factorization.

31511400021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3501266675 (or 3501266672 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

Adding to 31511400021 its reverse (12000411513), we get a palindrome (43511811534).

The spelling of 31511400021 in words is "thirty-one billion, five hundred eleven million, four hundred thousand, twenty-one".