21391606 has 16 divisors (see below), whose sum is σ = 33894000. Its totient is φ = 10097568.

The previous prime is 21391603. The next prime is 21391607. The reversal of 21391606 is 60619312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12456 + ... + 14068.

It is an arithmetic number, because the mean of its divisors is an integer number (2118375).

Almost surely, 2^21391606 is an apocalyptic number.

21391606 is a deficient number, since it is larger than the sum of its proper divisors (12502394).

21391606 is a wasteful number, since it uses less digits than its factorization.

21391606 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1983.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 21391606 is about 4625.1060528381. The cubic root of 21391606 is about 277.5968052270.

It can be divided in two parts, 213 and 91606, that added together give a palindrome (91819).

The spelling of 21391606 in words is "twenty-one million, three hundred ninety-one thousand, six hundred six".