21365669 has 4 divisors (see below), whose sum is σ = 23009196. Its totient is φ = 19722144.

The previous prime is 21365657. The next prime is 21365699. The reversal of 21365669 is 96656312.

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 2137444 + 19228225 = 1462^2 + 4385^2 .

It is not a de Polignac number, because 21365669 - 2²⁰ = 20317093 is a prime.

It is a super-2 number, since 2×21365669² = 912983623635122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365609) 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, 821744 + ... + 821769.

It is an arithmetic number, because the mean of its divisors is an integer number (5752299).

Almost surely, 2^21365669 is an apocalyptic number.

It is an amenable number.

21365669 is a deficient number, since it is larger than the sum of its proper divisors (1643527).

21365669 is a wasteful number, since it uses less digits than its factorization.

21365669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1643526.

The product of its digits is 58320, while the sum is 38.

The square root of 21365669 is about 4622.3012666852. The cubic root of 21365669 is about 277.4845658705.

The spelling of 21365669 in words is "twenty-one million, three hundred sixty-five thousand, six hundred sixty-nine".