21292891 has 4 divisors (see below), whose sum is σ = 22545432. Its totient is φ = 20040352.

The previous prime is 21292867. The next prime is 21292897. The reversal of 21292891 is 19829212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21292891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21292897) 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, 626245 + ... + 626278.

It is an arithmetic number, because the mean of its divisors is an integer number (5636358).

Almost surely, 2^21292891 is an apocalyptic number.

21292891 is a deficient number, since it is larger than the sum of its proper divisors (1252541).

21292891 is a wasteful number, since it uses less digits than its factorization.

21292891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1252540.

The product of its digits is 5184, while the sum is 34.

The square root of 21292891 is about 4614.4220656546. The cubic root of 21292891 is about 277.1691417028.

The spelling of 21292891 in words is "twenty-one million, two hundred ninety-two thousand, eight hundred ninety-one".