21505313031 has 16 divisors (see below), whose sum is σ = 29026214784. Its totient is φ = 14160726944.

The previous prime is 21505313023. The next prime is 21505313033. The reversal of 21505313031 is 13031350512.

It is not a de Polignac number, because 21505313031 - 2³ = 21505313023 is a prime.

It is a super-2 number, since 2×21505313031² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21505312992 and 21505313010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505313033) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1415980 + ... + 1431086.

It is an arithmetic number, because the mean of its divisors is an integer number (1814138424).

Almost surely, 2^21505313031 is an apocalyptic number.

21505313031 is a deficient number, since it is larger than the sum of its proper divisors (7520901753).

21505313031 is a wasteful number, since it uses less digits than its factorization.

21505313031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20910.

The product of its (nonzero) digits is 1350, while the sum is 24.

Adding to 21505313031 its reverse (13031350512), we get a palindrome (34536663543).

The spelling of 21505313031 in words is "twenty-one billion, five hundred five million, three hundred thirteen thousand, thirty-one".