21528891 has 6 divisors (see below), whose sum is σ = 31097300. Its totient is φ = 14352588.

The previous prime is 21528889. The next prime is 21528893. The reversal of 21528891 is 19882512.

It is an interprime number because it is at equal distance from previous prime (21528889) and next prime (21528893).

It is not a de Polignac number, because 21528891 - 2¹ = 21528889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21528893) 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, 1196041 + ... + 1196058.

Almost surely, 2^21528891 is an apocalyptic number.

21528891 is a deficient number, since it is larger than the sum of its proper divisors (9568409).

21528891 is a wasteful number, since it uses less digits than its factorization.

21528891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2392105 (or 2392102 counting only the distinct ones).

The product of its digits is 11520, while the sum is 36.

The square root of 21528891 is about 4639.9235985089. The cubic root of 21528891 is about 278.1893840928.

The spelling of 21528891 in words is "twenty-one million, five hundred twenty-eight thousand, eight hundred ninety-one".