21164999 has 4 divisors (see below), whose sum is σ = 21737064. Its totient is φ = 20592936.

The previous prime is 21164989. The next prime is 21165007. The reversal of 21164999 is 99946112.

It is a happy number.

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 21164999 - 2²⁴ = 4387783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164929) 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, 285977 + ... + 286050.

It is an arithmetic number, because the mean of its divisors is an integer number (5434266).

Almost surely, 2^21164999 is an apocalyptic number.

21164999 is a deficient number, since it is larger than the sum of its proper divisors (572065).

21164999 is an equidigital number, since it uses as much as digits as its factorization.

21164999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 572064.

The product of its digits is 34992, while the sum is 41.

The square root of 21164999 is about 4600.5433374766. The cubic root of 21164999 is about 276.6131044196.

The spelling of 21164999 in words is "twenty-one million, one hundred sixty-four thousand, nine hundred ninety-nine".