21351724 has 24 divisors (see below), whose sum is σ = 38485440. Its totient is φ = 10359936.

The previous prime is 21351721. The next prime is 21351749. The reversal of 21351724 is 42715312.

It is a happy number.

It is a super-2 number, since 2×21351724² = 911792235544352, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21351721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25342 + ... + 26170.

It is an arithmetic number, because the mean of its divisors is an integer number (1603560).

Almost surely, 2^21351724 is an apocalyptic number.

It is an amenable number.

21351724 is a deficient number, since it is larger than the sum of its proper divisors (17133716).

21351724 is a wasteful number, since it uses less digits than its factorization.

21351724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1017 (or 1015 counting only the distinct ones).

The product of its digits is 1680, while the sum is 25.

The square root of 21351724 is about 4620.7925727087. The cubic root of 21351724 is about 277.4241829507.

The spelling of 21351724 in words is "twenty-one million, three hundred fifty-one thousand, seven hundred twenty-four".