21247724 has 6 divisors (see below), whose sum is σ = 37183524. Its totient is φ = 10623860.

The previous prime is 21247693. The next prime is 21247727. The reversal of 21247724 is 42774212.

It is not an unprimeable number, because it can be changed into a prime (21247727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2655962 + ... + 2655969.

It is an arithmetic number, because the mean of its divisors is an integer number (6197254).

Almost surely, 2^21247724 is an apocalyptic number.

It is an amenable number.

21247724 is a deficient number, since it is larger than the sum of its proper divisors (15935800).

21247724 is a wasteful number, since it uses less digits than its factorization.

21247724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5311935 (or 5311933 counting only the distinct ones).

The product of its digits is 6272, while the sum is 29.

The square root of 21247724 is about 4609.5253551749. The cubic root of 21247724 is about 276.9730236516.

The spelling of 21247724 in words is "twenty-one million, two hundred forty-seven thousand, seven hundred twenty-four".