21704724 has 18 divisors (see below), whose sum is σ = 54864810. Its totient is φ = 7234896.

The previous prime is 21704693. The next prime is 21704737. The reversal of 21704724 is 42740712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18922500 + 2782224 = 4350^2 + 1668^2 .

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 301419 + ... + 301490.

It is an arithmetic number, because the mean of its divisors is an integer number (3048045).

Almost surely, 2^21704724 is an apocalyptic number.

It is an amenable number.

21704724 is an abundant number, since it is smaller than the sum of its proper divisors (33160086).

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

21704724 is a wasteful number, since it uses less digits than its factorization.

21704724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 602919 (or 602914 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21704724 is about 4658.8329010601. The cubic root of 21704724 is about 278.9446839886.

The spelling of 21704724 in words is "twenty-one million, seven hundred four thousand, seven hundred twenty-four".