21000965 has 12 divisors (see below), whose sum is σ = 25562124. Its totient is φ = 16563456.

The previous prime is 21000953. The next prime is 21000977. The reversal of 21000965 is 56900012.

It is an interprime number because it is at equal distance from previous prime (21000953) and next prime (21000977).

It can be written as a sum of positive squares in 2 ways, for example, as 7214596 + 13786369 = 2686^2 + 3713^2 .

It is not a de Polignac number, because 21000965 - 2⁸ = 21000709 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 21000965.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 30869 + ... + 31541.

It is an arithmetic number, because the mean of its divisors is an integer number (2130177).

Almost surely, 2^21000965 is an apocalyptic number.

It is an amenable number.

21000965 is a deficient number, since it is larger than the sum of its proper divisors (4561159).

21000965 is an frugal number, since it uses more digits than its factorization.

21000965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 836 (or 757 counting only the distinct ones).

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21000965 is about 4582.6809838783. The cubic root of 21000965 is about 275.8966435445.

Adding to 21000965 its reverse (56900012), we get a palindrome (77900977).

The spelling of 21000965 in words is "twenty-one million, nine hundred sixty-five", and thus it is an aban number.