21002331531 has 4 divisors (see below), whose sum is σ = 28003108712. Its totient is φ = 14001554352.

The previous prime is 21002331523. The next prime is 21002331547. The reversal of 21002331531 is 13513320012.

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

It is not a de Polignac number, because 21002331531 - 2³ = 21002331523 is a prime.

It is a super-2 number, since 2×21002331531² (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 = 21002331498 and 21002331507.

It is not an unprimeable number, because it can be changed into a prime (21002331551) 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, 3500388586 + ... + 3500388591.

It is an arithmetic number, because the mean of its divisors is an integer number (7000777178).

Almost surely, 2^21002331531 is an apocalyptic number.

21002331531 is a deficient number, since it is larger than the sum of its proper divisors (7000777181).

21002331531 is an equidigital number, since it uses as much as digits as its factorization.

21002331531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7000777180.

The product of its (nonzero) digits is 540, while the sum is 21.

Adding to 21002331531 its reverse (13513320012), we get a palindrome (34515651543).

The spelling of 21002331531 in words is "twenty-one billion, two million, three hundred thirty-one thousand, five hundred thirty-one".