21000342531 has 24 divisors (see below), whose sum is σ = 33124040640. Its totient is φ = 11796797712.

The previous prime is 21000342523. The next prime is 21000342541. The reversal of 21000342531 is 13524300012.

It is not a de Polignac number, because 21000342531 - 2³ = 21000342523 is a prime.

It is a super-2 number, since 2×21000342531² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21000342498 and 21000342507.

It is not an unprimeable number, because it can be changed into a prime (21000342511) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1202001 + ... + 1219346.

It is an arithmetic number, because the mean of its divisors is an integer number (1380168360).

Almost surely, 2^21000342531 is an apocalyptic number.

21000342531 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21000342531 is a deficient number, since it is larger than the sum of its proper divisors (12123698109).

21000342531 is a wasteful number, since it uses less digits than its factorization.

21000342531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2421423 (or 2421416 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

Adding to 21000342531 its reverse (13524300012), we get a palindrome (34524642543).

The spelling of 21000342531 in words is "twenty-one billion, three hundred forty-two thousand, five hundred thirty-one".