21258391 has 8 divisors (see below), whose sum is σ = 26504064. Its totient is φ = 16564920.

The previous prime is 21258373. The next prime is 21258401. The reversal of 21258391 is 19385212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21258391 - 2¹³ = 21250199 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 (21258301) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 137965 + ... + 138118.

It is an arithmetic number, because the mean of its divisors is an integer number (3313008).

Almost surely, 2^21258391 is an apocalyptic number.

21258391 is a deficient number, since it is larger than the sum of its proper divisors (5245673).

21258391 is a wasteful number, since it uses less digits than its factorization.

21258391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 276101.

The product of its digits is 4320, while the sum is 31.

The square root of 21258391 is about 4610.6822705539. The cubic root of 21258391 is about 277.0193655087.

The spelling of 21258391 in words is "twenty-one million, two hundred fifty-eight thousand, three hundred ninety-one".