21020013031 has 4 divisors (see below), whose sum is σ = 21020538672. Its totient is φ = 21019487392.

The previous prime is 21020013023. The next prime is 21020013067. The reversal of 21020013031 is 13031002012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21020013031 - 2³ = 21020013023 is a prime.

It is a super-2 number, since 2×21020013031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020013071) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 197410 + ... + 284623.

It is an arithmetic number, because the mean of its divisors is an integer number (5255134668).

Almost surely, 2^21020013031 is an apocalyptic number.

21020013031 is a deficient number, since it is larger than the sum of its proper divisors (525641).

21020013031 is an equidigital number, since it uses as much as digits as its factorization.

21020013031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525640.

The product of its (nonzero) digits is 36, while the sum is 13.

Adding to 21020013031 its reverse (13031002012), we get a palindrome (34051015043).

The spelling of 21020013031 in words is "twenty-one billion, twenty million, thirteen thousand, thirty-one".