21729252 has 12 divisors (see below), whose sum is σ = 50701616. Its totient is φ = 7243080.

The previous prime is 21729229. The next prime is 21729263. The reversal of 21729252 is 25292712.

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

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 905374 + ... + 905397.

Almost surely, 2^21729252 is an apocalyptic number.

It is an amenable number.

21729252 is an abundant number, since it is smaller than the sum of its proper divisors (28972364).

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

21729252 is a wasteful number, since it uses less digits than its factorization.

21729252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1810778 (or 1810776 counting only the distinct ones).

The product of its digits is 5040, while the sum is 30.

The square root of 21729252 is about 4661.4645767184. The cubic root of 21729252 is about 279.0497207157.

The spelling of 21729252 in words is "twenty-one million, seven hundred twenty-nine thousand, two hundred fifty-two".