21939766 has 4 divisors (see below), whose sum is σ = 32909652. Its totient is φ = 10969882.

The previous prime is 21939763. The next prime is 21939767. The reversal of 21939766 is 66793912.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21939763) 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 as a sum of consecutive naturals, namely, 5484940 + ... + 5484943.

It is an arithmetic number, because the mean of its divisors is an integer number (8227413).

Almost surely, 2^21939766 is an apocalyptic number.

21939766 is a deficient number, since it is larger than the sum of its proper divisors (10969886).

21939766 is a wasteful number, since it uses less digits than its factorization.

21939766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10969885.

The product of its digits is 122472, while the sum is 43.

The square root of 21939766 is about 4683.9903928168. The cubic root of 21939766 is about 279.9479750281.

The spelling of 21939766 in words is "twenty-one million, nine hundred thirty-nine thousand, seven hundred sixty-six".