21131012020 has 24 divisors (see below), whose sum is σ = 45212394024. Its totient is φ = 8292925056.

The previous prime is 21131012009. The next prime is 21131012029. The reversal of 21131012020 is 2021013112.

It can be written as a sum of positive squares in 4 ways, for example, as 503733136 + 20627278884 = 22444^2 + 143622^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21131012029) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9966399 + ... + 9968518.

It is an arithmetic number, because the mean of its divisors is an integer number (1883849751).

Almost surely, 2^21131012020 is an apocalyptic number.

21131012020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21131012020 is an abundant number, since it is smaller than the sum of its proper divisors (24081382004).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21131012020 is a wasteful number, since it uses less digits than its factorization.

21131012020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19934979 (or 19934977 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 21131012020 its reverse (2021013112), we get a palindrome (23152025132).

The spelling of 21131012020 in words is "twenty-one billion, one hundred thirty-one million, twelve thousand, twenty".