21247790 has 16 divisors (see below), whose sum is σ = 40496112. Its totient is φ = 7999104.

The previous prime is 21247789. The next prime is 21247819. The reversal of 21247790 is 9774212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62324 + ... + 62663.

It is an arithmetic number, because the mean of its divisors is an integer number (2531007).

Almost surely, 2^21247790 is an apocalyptic number.

21247790 is a deficient number, since it is larger than the sum of its proper divisors (19248322).

21247790 is a wasteful number, since it uses less digits than its factorization.

21247790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 125011.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21247790 is about 4609.5325142578. The cubic root of 21247790 is about 276.9733104305.

The spelling of 21247790 in words is "twenty-one million, two hundred forty-seven thousand, seven hundred ninety".