21258551 has 8 divisors (see below), whose sum is σ = 22592160. Its totient is φ = 20003424.

The previous prime is 21258547. The next prime is 21258563. The reversal of 21258551 is 15585212.

It is not a de Polignac number, because 21258551 - 2² = 21258547 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 (21258151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2750 + ... + 7076.

It is an arithmetic number, because the mean of its divisors is an integer number (2824020).

Almost surely, 2^21258551 is an apocalyptic number.

21258551 is a deficient number, since it is larger than the sum of its proper divisors (1333609).

21258551 is an frugal number, since it uses more digits than its factorization.

21258551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4378 (or 4344 counting only the distinct ones).

The product of its digits is 4000, while the sum is 29.

The square root of 21258551 is about 4610.6996215325. The cubic root of 21258551 is about 277.0200604968.

The spelling of 21258551 in words is "twenty-one million, two hundred fifty-eight thousand, five hundred fifty-one".