21764638 has 16 divisors (see below), whose sum is σ = 37407744. Its totient is φ = 9303480.

The previous prime is 21764627. The next prime is 21764651. The reversal of 21764638 is 83646712.

It is a junction number, because it is equal to n+sod(n) for n = 21764597 and 21764606.

It is a congruent number.

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, 4231 + ... + 7837.

It is an arithmetic number, because the mean of its divisors is an integer number (2337984).

Almost surely, 2^21764638 is an apocalyptic number.

21764638 is a deficient number, since it is larger than the sum of its proper divisors (15643106).

21764638 is a wasteful number, since it uses less digits than its factorization.

21764638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4047.

The product of its digits is 48384, while the sum is 37.

The square root of 21764638 is about 4665.2586209127. The cubic root of 21764638 is about 279.2011156815.

The spelling of 21764638 in words is "twenty-one million, seven hundred sixty-four thousand, six hundred thirty-eight".