21397790 has 32 divisors (see below), whose sum is σ = 39584160. Its totient is φ = 8325504.

The previous prime is 21397787. The next prime is 21397807. The reversal of 21397790 is 9779312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 72884 + ... + 73176.

It is an arithmetic number, because the mean of its divisors is an integer number (1237005).

Almost surely, 2^21397790 is an apocalyptic number.

21397790 is a deficient number, since it is larger than the sum of its proper divisors (18186370).

21397790 is a wasteful number, since it uses less digits than its factorization.

21397790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 476.

The product of its (nonzero) digits is 23814, while the sum is 38.

The square root of 21397790 is about 4625.7745297409. The cubic root of 21397790 is about 277.6235523733.

The spelling of 21397790 in words is "twenty-one million, three hundred ninety-seven thousand, seven hundred ninety".