21765890 has 16 divisors (see below), whose sum is σ = 39287808. Its totient is φ = 8682096.

The previous prime is 21765859. The next prime is 21765893. The reversal of 21765890 is 9856712.

It is not an unprimeable number, because it can be changed into a prime (21765893) 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, 989 + ... + 6671.

It is an arithmetic number, because the mean of its divisors is an integer number (2455488).

Almost surely, 2^21765890 is an apocalyptic number.

21765890 is a deficient number, since it is larger than the sum of its proper divisors (17521918).

21765890 is a wasteful number, since it uses less digits than its factorization.

21765890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6073.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 21765890 is about 4665.3928023265. The cubic root of 21765890 is about 279.2064692141.

The spelling of 21765890 in words is "twenty-one million, seven hundred sixty-five thousand, eight hundred ninety".