21164791 has 4 divisors (see below), whose sum is σ = 21192472. Its totient is φ = 21137112.

The previous prime is 21164789. The next prime is 21164797. The reversal of 21164791 is 19746112.

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 21164791 - 2¹ = 21164789 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 (21164797) 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, 12660 + ... + 14233.

It is an arithmetic number, because the mean of its divisors is an integer number (5298118).

Almost surely, 2^21164791 is an apocalyptic number.

21164791 is a deficient number, since it is larger than the sum of its proper divisors (27681).

21164791 is an equidigital number, since it uses as much as digits as its factorization.

21164791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27680.

The product of its digits is 3024, while the sum is 31.

The square root of 21164791 is about 4600.5207313955. The cubic root of 21164791 is about 276.6121982739.

The spelling of 21164791 in words is "twenty-one million, one hundred sixty-four thousand, seven hundred ninety-one".