21319765 has 4 divisors (see below), whose sum is σ = 25583724. Its totient is φ = 17055808.

The previous prime is 21319763. The next prime is 21319769. The reversal of 21319765 is 56791312.

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 5391684 + 15928081 = 2322^2 + 3991^2 .

It is a cyclic number.

It is not a de Polignac number, because 21319765 - 2¹ = 21319763 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 21319765.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21319763) 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, 2131972 + ... + 2131981.

It is an arithmetic number, because the mean of its divisors is an integer number (6395931).

Almost surely, 2^21319765 is an apocalyptic number.

It is an amenable number.

21319765 is a deficient number, since it is larger than the sum of its proper divisors (4263959).

21319765 is an equidigital number, since it uses as much as digits as its factorization.

21319765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4263958.

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

The square root of 21319765 is about 4617.3331047261. Note that the first 3 decimals coincide. The cubic root of 21319765 is about 277.2856987897.

The spelling of 21319765 in words is "twenty-one million, three hundred nineteen thousand, seven hundred sixty-five".