21291552 has 96 divisors (see below), whose sum is σ = 65419200. Its totient is φ = 6718464.

The previous prime is 21291547. The next prime is 21291593. The reversal of 21291552 is 25519212.

21291552 is a `hidden beast` number, since 21 + 2 + 91 + 552 = 666.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15768 + ... + 17064.

It is an arithmetic number, because the mean of its divisors is an integer number (681450).

Almost surely, 2^21291552 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21291552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32709600).

21291552 is an abundant number, since it is smaller than the sum of its proper divisors (44127648).

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

21291552 is a wasteful number, since it uses less digits than its factorization.

21291552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1335 (or 1321 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 21291552 is about 4614.2769747816. The cubic root of 21291552 is about 277.1633316689.

The spelling of 21291552 in words is "twenty-one million, two hundred ninety-one thousand, five hundred fifty-two".