21957830 has 16 divisors (see below), whose sum is σ = 39810960. Its totient is φ = 8719392.

The previous prime is 21957811. The next prime is 21957841. The reversal of 21957830 is 3875912.

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, 6509 + ... + 9288.

It is an arithmetic number, because the mean of its divisors is an integer number (2488185).

Almost surely, 2^21957830 is an apocalyptic number.

21957830 is a deficient number, since it is larger than the sum of its proper divisors (17853130).

21957830 is a wasteful number, since it uses less digits than its factorization.

21957830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15943.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21957830 is about 4685.9182664660. The cubic root of 21957830 is about 280.0247852209.

The spelling of 21957830 in words is "twenty-one million, nine hundred fifty-seven thousand, eight hundred thirty".