21291252 has 12 divisors (see below), whose sum is σ = 49679616. Its totient is φ = 7097080.

The previous prime is 21291247. The next prime is 21291269. The reversal of 21291252 is 25219212.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 887124 + ... + 887147.

It is an arithmetic number, because the mean of its divisors is an integer number (4139968).

Almost surely, 2^21291252 is an apocalyptic number.

It is an amenable number.

21291252 is an abundant number, since it is smaller than the sum of its proper divisors (28388364).

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

21291252 is a wasteful number, since it uses less digits than its factorization.

21291252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1774278 (or 1774276 counting only the distinct ones).

The product of its digits is 720, while the sum is 24.

The square root of 21291252 is about 4614.2444668656. The cubic root of 21291252 is about 277.1620299102.

The spelling of 21291252 in words is "twenty-one million, two hundred ninety-one thousand, two hundred fifty-two".