21213645031 has 4 divisors (see below), whose sum is σ = 21213991552. Its totient is φ = 21213298512.

The previous prime is 21213645023. The next prime is 21213645059. The reversal of 21213645031 is 13054631212.

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 21213645031 - 2³ = 21213645023 is a prime.

It is a super-2 number, since 2×21213645031² (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 (21213645001) 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, 54126 + ... + 212971.

It is an arithmetic number, because the mean of its divisors is an integer number (5303497888).

Almost surely, 2^21213645031 is an apocalyptic number.

21213645031 is a deficient number, since it is larger than the sum of its proper divisors (346521).

21213645031 is an equidigital number, since it uses as much as digits as its factorization.

21213645031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 346520.

The product of its (nonzero) digits is 4320, while the sum is 28.

The spelling of 21213645031 in words is "twenty-one billion, two hundred thirteen million, six hundred forty-five thousand, thirty-one".