21165963 has 64 divisors (see below), whose sum is σ = 37330944. Its totient is φ = 10368000.

The previous prime is 21165941. The next prime is 21165967. The reversal of 21165963 is 36956112.

It is a happy number.

It is not a de Polignac number, because 21165963 - 2¹⁰ = 21164939 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21165967) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 346953 + ... + 347013.

It is an arithmetic number, because the mean of its divisors is an integer number (583296).

Almost surely, 2^21165963 is an apocalyptic number.

21165963 is a deficient number, since it is larger than the sum of its proper divisors (16164981).

21165963 is a wasteful number, since it uses less digits than its factorization.

21165963 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156.

The product of its digits is 9720, while the sum is 33.

The square root of 21165963 is about 4600.6481065172. The cubic root of 21165963 is about 276.6173039785.

The spelling of 21165963 in words is "twenty-one million, one hundred sixty-five thousand, nine hundred sixty-three".