21887128 has 16 divisors (see below), whose sum is σ = 42148080. Its totient is φ = 10647648.

The previous prime is 21887119. The next prime is 21887149. The reversal of 21887128 is 82178812.

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

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 3 ways as a sum of consecutive naturals, for example, 36676 + ... + 37267.

It is an arithmetic number, because the mean of its divisors is an integer number (2634255).

Almost surely, 2^21887128 is an apocalyptic number.

It is an amenable number.

21887128 is a deficient number, since it is larger than the sum of its proper divisors (20260952).

21887128 is a wasteful number, since it uses less digits than its factorization.

21887128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73986 (or 73982 counting only the distinct ones).

The product of its digits is 14336, while the sum is 37.

The square root of 21887128 is about 4678.3680915465. The cubic root of 21887128 is about 279.7239115314.

It can be divided in two parts, 2188 and 7128, that added together give a triangular number (9316 = T₁₃₆).

The spelling of 21887128 in words is "twenty-one million, eight hundred eighty-seven thousand, one hundred twenty-eight".