21391045 has 16 divisors (see below), whose sum is σ = 27804672. Its totient is φ = 15704640.

The previous prime is 21391033. The next prime is 21391057. The reversal of 21391045 is 54019312.

It is an interprime number because it is at equal distance from previous prime (21391033) and next prime (21391057).

It is not a de Polignac number, because 21391045 - 2¹⁵ = 21358277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11554 + ... + 13276.

It is an arithmetic number, because the mean of its divisors is an integer number (1737792).

Almost surely, 2^21391045 is an apocalyptic number.

It is an amenable number.

21391045 is a deficient number, since it is larger than the sum of its proper divisors (6413627).

21391045 is a wasteful number, since it uses less digits than its factorization.

21391045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1932.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21391045 is about 4625.0454051825. The cubic root of 21391045 is about 277.5943785248.

The spelling of 21391045 in words is "twenty-one million, three hundred ninety-one thousand, forty-five".