21831724 has 6 divisors (see below), whose sum is σ = 38205524. Its totient is φ = 10915860.

The previous prime is 21831701. The next prime is 21831769. The reversal of 21831724 is 42713812.

It is a junction number, because it is equal to n+sod(n) for n = 21831692 and 21831701.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2728962 + ... + 2728969.

Almost surely, 2^21831724 is an apocalyptic number.

It is an amenable number.

21831724 is a deficient number, since it is larger than the sum of its proper divisors (16373800).

21831724 is a wasteful number, since it uses less digits than its factorization.

21831724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5457935 (or 5457933 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 21831724 is about 4672.4430440616. The cubic root of 21831724 is about 279.4876856421.

The spelling of 21831724 in words is "twenty-one million, eight hundred thirty-one thousand, seven hundred twenty-four".