21839765 has 16 divisors (see below), whose sum is σ = 27475200. Its totient is φ = 16665616.

The previous prime is 21839737. The next prime is 21839767. The reversal of 21839765 is 56793812.

It is not a de Polignac number, because 21839765 - 2²⁰ = 20791189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21839767) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60656 + ... + 61014.

It is an arithmetic number, because the mean of its divisors is an integer number (1717200).

Almost surely, 2^21839765 is an apocalyptic number.

It is an amenable number.

21839765 is a deficient number, since it is larger than the sum of its proper divisors (5635435).

21839765 is an frugal number, since it uses more digits than its factorization.

21839765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433 (or 387 counting only the distinct ones).

The product of its digits is 90720, while the sum is 41.

The square root of 21839765 is about 4673.3034354726. The cubic root of 21839765 is about 279.5219948065.

The spelling of 21839765 in words is "twenty-one million, eight hundred thirty-nine thousand, seven hundred sixty-five".