21493855 has 16 divisors (see below), whose sum is σ = 26659584. Its totient is φ = 16623360.

The previous prime is 21493853. The next prime is 21493867. The reversal of 21493855 is 55839412.

It is not a de Polignac number, because 21493855 - 2¹ = 21493853 is a prime.

It is a super-2 number, since 2×21493855² = 923971605522050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21493853) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40995 + ... + 41515.

It is an arithmetic number, because the mean of its divisors is an integer number (1666224).

Almost surely, 2^21493855 is an apocalyptic number.

21493855 is a deficient number, since it is larger than the sum of its proper divisors (5165729).

21493855 is a wasteful number, since it uses less digits than its factorization.

21493855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 786.

The product of its digits is 43200, while the sum is 37.

The square root of 21493855 is about 4636.1465680024. The cubic root of 21493855 is about 278.0383941934.

The spelling of 21493855 in words is "twenty-one million, four hundred ninety-three thousand, eight hundred fifty-five".