21390610 has 16 divisors (see below), whose sum is σ = 38808576. Its totient is φ = 8488368.

The previous prime is 21390601. The next prime is 21390613. The reversal of 21390610 is 1609312.

It is not an unprimeable number, because it can be changed into a prime (21390613) 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, 7152 + ... + 9691.

It is an arithmetic number, because the mean of its divisors is an integer number (2425536).

Almost surely, 2^21390610 is an apocalyptic number.

21390610 is a deficient number, since it is larger than the sum of its proper divisors (17417966).

21390610 is a wasteful number, since it uses less digits than its factorization.

21390610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16977.

The product of its (nonzero) digits is 324, while the sum is 22.

The square root of 21390610 is about 4624.9983783781. The cubic root of 21390610 is about 277.5924968282.

Adding to 21390610 its reverse (1609312), we get a palindrome (22999922).

The spelling of 21390610 in words is "twenty-one million, three hundred ninety thousand, six hundred ten".