21011608531 has 4 divisors (see below), whose sum is σ = 21925156752. Its totient is φ = 20098060312.

The previous prime is 21011608529. The next prime is 21011608549. The reversal of 21011608531 is 13580611012.

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 21011608531 - 2¹ = 21011608529 is a prime.

It is a super-2 number, since 2×21011608531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21011608531.

It is not an unprimeable number, because it can be changed into a prime (21011608571) 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, 456774076 + ... + 456774121.

It is an arithmetic number, because the mean of its divisors is an integer number (5481289188).

Almost surely, 2^21011608531 is an apocalyptic number.

21011608531 is a deficient number, since it is larger than the sum of its proper divisors (913548221).

21011608531 is an equidigital number, since it uses as much as digits as its factorization.

21011608531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913548220.

The product of its (nonzero) digits is 1440, while the sum is 28.

The spelling of 21011608531 in words is "twenty-one billion, eleven million, six hundred eight thousand, five hundred thirty-one".