21385872 has 30 divisors (see below), whose sum is σ = 59851142. Its totient is φ = 7128576.

The previous prime is 21385867. The next prime is 21385879. The reversal of 21385872 is 27858312.

It can be written as a sum of positive squares in only one way, i.e., 10732176 + 10653696 = 3276^2 + 3264^2 .

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21385879) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 74113 + ... + 74400.

Almost surely, 2^21385872 is an apocalyptic number.

It is an amenable number.

21385872 is an abundant number, since it is smaller than the sum of its proper divisors (38465270).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21385872 is a wasteful number, since it uses less digits than its factorization.

21385872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 148527 (or 148518 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 21385872 is about 4624.4861336153. The cubic root of 21385872 is about 277.5719998224.

It can be divided in two parts, 213858 and 72, that multiplied together give a square (15397776 = 3924²).

The spelling of 21385872 in words is "twenty-one million, three hundred eighty-five thousand, eight hundred seventy-two".