21149965 has 4 divisors (see below), whose sum is σ = 25379964. Its totient is φ = 16919968.

The previous prime is 21149951. The next prime is 21149969. The reversal of 21149965 is 56994112.

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 3493161 + 17656804 = 1869^2 + 4202^2 .

It is a cyclic number.

It is not a de Polignac number, because 21149965 - 2⁷ = 21149837 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 (21149969) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2114992 + ... + 2115001.

It is an arithmetic number, because the mean of its divisors is an integer number (6344991).

Almost surely, 2^21149965 is an apocalyptic number.

It is an amenable number.

21149965 is a deficient number, since it is larger than the sum of its proper divisors (4229999).

21149965 is an equidigital number, since it uses as much as digits as its factorization.

21149965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4229998.

The product of its digits is 19440, while the sum is 37.

The square root of 21149965 is about 4598.9091097781. The cubic root of 21149965 is about 276.5475939597.

It can be divided in two parts, 211 and 49965, that added together give a square (50176 = 224²).

The spelling of 21149965 in words is "twenty-one million, one hundred forty-nine thousand, nine hundred sixty-five".