21393724 has 12 divisors (see below), whose sum is σ = 40842648. Its totient is φ = 9724400.

The previous prime is 21393709. The next prime is 21393727. The reversal of 21393724 is 42739312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21393727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 243067 + ... + 243154.

It is an arithmetic number, because the mean of its divisors is an integer number (3403554).

Almost surely, 2^21393724 is an apocalyptic number.

It is an amenable number.

21393724 is a deficient number, since it is larger than the sum of its proper divisors (19448924).

21393724 is a wasteful number, since it uses less digits than its factorization.

21393724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486236 (or 486234 counting only the distinct ones).

The product of its digits is 9072, while the sum is 31.

The square root of 21393724 is about 4625.3350148935. The cubic root of 21393724 is about 277.6059666184.

The spelling of 21393724 in words is "twenty-one million, three hundred ninety-three thousand, seven hundred twenty-four".