21665494 has 32 divisors (see below), whose sum is σ = 35640000. Its totient is φ = 9846144.

The previous prime is 21665489. The next prime is 21665503. The reversal of 21665494 is 49456612.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 145332 + ... + 145480.

It is an arithmetic number, because the mean of its divisors is an integer number (1113750).

Almost surely, 2^21665494 is an apocalyptic number.

21665494 is a deficient number, since it is larger than the sum of its proper divisors (13974506).

21665494 is a wasteful number, since it uses less digits than its factorization.

21665494 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312.

The product of its digits is 51840, while the sum is 37.

The square root of 21665494 is about 4654.6207149455. The cubic root of 21665494 is about 278.7765239831.

The spelling of 21665494 in words is "twenty-one million, six hundred sixty-five thousand, four hundred ninety-four".