21358172 has 24 divisors (see below), whose sum is σ = 40906992. Its totient is φ = 9676800.

The previous prime is 21358159. The next prime is 21358187. The reversal of 21358172 is 27185312.

It is a super-2 number, since 2×21358172² = 912343022363168, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17948 + ... + 19100.

It is an arithmetic number, because the mean of its divisors is an integer number (1704458).

Almost surely, 2^21358172 is an apocalyptic number.

21358172 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21358172 is a deficient number, since it is larger than the sum of its proper divisors (19548820).

21358172 is a wasteful number, since it uses less digits than its factorization.

21358172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1589 (or 1587 counting only the distinct ones).

The product of its digits is 3360, while the sum is 29.

The square root of 21358172 is about 4621.4902358438. The cubic root of 21358172 is about 277.4521065521.

It can be divided in two parts, 213 and 58172, that added together give a palindrome (58385).

The spelling of 21358172 in words is "twenty-one million, three hundred fifty-eight thousand, one hundred seventy-two".