21164531 has 4 divisors (see below), whose sum is σ = 22084752. Its totient is φ = 20244312.

The previous prime is 21164509. The next prime is 21164567. The reversal of 21164531 is 13546112.

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 21164531 - 2¹⁰ = 21163507 is a prime.

It is a super-2 number, since 2×21164531² = 895874744899922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 920197 = 21164531 / (2 + 1 + 1 + 6 + 4 + 5 + 3 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21164497 and 21164506.

It is not an unprimeable number, because it can be changed into a prime (21164501) 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, 460076 + ... + 460121.

It is an arithmetic number, because the mean of its divisors is an integer number (5521188).

Almost surely, 2^21164531 is an apocalyptic number.

21164531 is a deficient number, since it is larger than the sum of its proper divisors (920221).

21164531 is an equidigital number, since it uses as much as digits as its factorization.

21164531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 920220.

The product of its digits is 720, while the sum is 23.

The square root of 21164531 is about 4600.4924736380. The cubic root of 21164531 is about 276.6110655835.

The spelling of 21164531 in words is "twenty-one million, one hundred sixty-four thousand, five hundred thirty-one".