21309252 has 48 divisors (see below), whose sum is σ = 51788352. Its totient is φ = 6814080.

The previous prime is 21309221. The next prime is 21309257. The reversal of 21309252 is 25290312.

It is not an unprimeable number, because it can be changed into a prime (21309257) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31138 + ... + 31814.

It is an arithmetic number, because the mean of its divisors is an integer number (1078924).

Almost surely, 2^21309252 is an apocalyptic number.

It is an amenable number.

21309252 is an abundant number, since it is smaller than the sum of its proper divisors (30479100).

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

21309252 is a wasteful number, since it uses less digits than its factorization.

21309252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 788 (or 786 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 24.

The square root of 21309252 is about 4616.1945366286. The cubic root of 21309252 is about 277.2401137994.

Adding to 21309252 its reverse (25290312), we get a palindrome (46599564).

The spelling of 21309252 in words is "twenty-one million, three hundred nine thousand, two hundred fifty-two".