21540023031 has 4 divisors (see below), whose sum is σ = 28720030712. Its totient is φ = 14360015352.

The previous prime is 21540023003. The next prime is 21540023039. The reversal of 21540023031 is 13032004512.

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

It is not a de Polignac number, because 21540023031 - 2²⁷ = 21405805303 is a prime.

It is a super-2 number, since 2×21540023031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21540022989 and 21540023007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540023039) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3590003836 + ... + 3590003841.

It is an arithmetic number, because the mean of its divisors is an integer number (7180007678).

Almost surely, 2^21540023031 is an apocalyptic number.

21540023031 is a deficient number, since it is larger than the sum of its proper divisors (7180007681).

21540023031 is an equidigital number, since it uses as much as digits as its factorization.

21540023031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7180007680.

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

Adding to 21540023031 its reverse (13032004512), we get a palindrome (34572027543).

The spelling of 21540023031 in words is "twenty-one billion, five hundred forty million, twenty-three thousand, thirty-one".