21065765 has 16 divisors (see below), whose sum is σ = 29672832. Its totient is φ = 14053824.

The previous prime is 21065753. The next prime is 21065767. The reversal of 21065765 is 56756012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21065765 - 2⁶ = 21065701 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065767) 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, 6839 + ... + 9428.

It is an arithmetic number, because the mean of its divisors is an integer number (1854552).

Almost surely, 2^21065765 is an apocalyptic number.

It is an amenable number.

21065765 is a deficient number, since it is larger than the sum of its proper divisors (8607067).

21065765 is a wasteful number, since it uses less digits than its factorization.

21065765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16316.

The product of its (nonzero) digits is 12600, while the sum is 32.

The square root of 21065765 is about 4589.7456356535. The cubic root of 21065765 is about 276.1801185483.

The spelling of 21065765 in words is "twenty-one million, sixty-five thousand, seven hundred sixty-five".