21391010 has 16 divisors (see below), whose sum is σ = 38602872. Its totient is φ = 8534400.

The previous prime is 21390997. The next prime is 21391021. The reversal of 21391010 is 1019312.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 5764801 + 15626209 = 2401^2 + 3953^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21391010.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1670 + ... + 6750.

Almost surely, 2^21391010 is an apocalyptic number.

21391010 is a deficient number, since it is larger than the sum of its proper divisors (17211862).

21391010 is a wasteful number, since it uses less digits than its factorization.

21391010 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5509.

The product of its (nonzero) digits is 54, while the sum is 17.

The square root of 21391010 is about 4625.0416214343. The cubic root of 21391010 is about 277.5942271249.

The spelling of 21391010 in words is "twenty-one million, three hundred ninety-one thousand, ten".