21173965 has 4 divisors (see below), whose sum is σ = 25408764. Its totient is φ = 16939168.

The previous prime is 21173963. The next prime is 21173969. The reversal of 21173965 is 56937112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12489156 + 8684809 = 3534^2 + 2947^2 .

It is a cyclic number.

It is not a de Polignac number, because 21173965 - 2¹ = 21173963 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21173965.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21173963) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2117392 + ... + 2117401.

It is an arithmetic number, because the mean of its divisors is an integer number (6352191).

Almost surely, 2^21173965 is an apocalyptic number.

It is an amenable number.

21173965 is a deficient number, since it is larger than the sum of its proper divisors (4234799).

21173965 is an equidigital number, since it uses as much as digits as its factorization.

21173965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4234798.

The product of its digits is 11340, while the sum is 34.

The square root of 21173965 is about 4601.5176844167. The cubic root of 21173965 is about 276.6521588818.

The spelling of 21173965 in words is "twenty-one million, one hundred seventy-three thousand, nine hundred sixty-five".