21789252 has 18 divisors (see below), whose sum is σ = 55078478. Its totient is φ = 7263072.

The previous prime is 21789241. The next prime is 21789281. The reversal of 21789252 is 25298712.

It can be written as a sum of positive squares in only one way, i.e., 21399876 + 389376 = 4626^2 + 624^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 605257 = 21789252 / (2 + 1 + 7 + 8 + 9 + 2 + 5 + 2).

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 5 ways as a sum of consecutive naturals, for example, 302593 + ... + 302664.

Almost surely, 2^21789252 is an apocalyptic number.

It is an amenable number.

21789252 is an abundant number, since it is smaller than the sum of its proper divisors (33289226).

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

21789252 is a wasteful number, since it uses less digits than its factorization.

21789252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 605267 (or 605262 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21789252 is about 4667.8958857284. The cubic root of 21789252 is about 279.3063271295.

The spelling of 21789252 in words is "twenty-one million, seven hundred eighty-nine thousand, two hundred fifty-two".