21426391 has 4 divisors (see below), whose sum is σ = 24487312. Its totient is φ = 18365472.

The previous prime is 21426371. The next prime is 21426401. The reversal of 21426391 is 19362412.

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 21426391 - 2⁵ = 21426359 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 (21426371) 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, 1530450 + ... + 1530463.

It is an arithmetic number, because the mean of its divisors is an integer number (6121828).

Almost surely, 2^21426391 is an apocalyptic number.

21426391 is a deficient number, since it is larger than the sum of its proper divisors (3060921).

21426391 is an equidigital number, since it uses as much as digits as its factorization.

21426391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3060920.

The product of its digits is 2592, while the sum is 28.

The square root of 21426391 is about 4628.8649796683. The cubic root of 21426391 is about 277.7471909373.

The spelling of 21426391 in words is "twenty-one million, four hundred twenty-six thousand, three hundred ninety-one".