21965965 has 12 divisors (see below), whose sum is σ = 30663036. Its totient is φ = 15062208.

The previous prime is 21965959. The next prime is 21965969. The reversal of 21965965 is 56956912.

It can be written as a sum of positive squares in 2 ways, for example, as 16597476 + 5368489 = 4074^2 + 2317^2 .

It is not a de Polignac number, because 21965965 - 2⁷ = 21965837 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21965969) 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 in 11 ways as a sum of consecutive naturals, for example, 44584 + ... + 45073.

It is an arithmetic number, because the mean of its divisors is an integer number (2555253).

Almost surely, 2^21965965 is an apocalyptic number.

It is an amenable number.

21965965 is a deficient number, since it is larger than the sum of its proper divisors (8697071).

21965965 is an equidigital number, since it uses as much as digits as its factorization.

21965965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89676 (or 89669 counting only the distinct ones).

The product of its digits is 145800, while the sum is 43.

The square root of 21965965 is about 4686.7862123208. The cubic root of 21965965 is about 280.0593624138.

It can be divided in two parts, 21 and 965965, that multiplied together give a triangular number (20285265 = T₆₃₆₉).

The spelling of 21965965 in words is "twenty-one million, nine hundred sixty-five thousand, nine hundred sixty-five".