21365345 has 16 divisors (see below), whose sum is σ = 27336528. Its totient is φ = 15974400.

The previous prime is 21365303. The next prime is 21365347. The reversal of 21365345 is 54356312.

It can be written as a sum of positive squares in 8 ways, for example, as 2347024 + 19018321 = 1532^2 + 4361^2 .

It is not a de Polignac number, because 21365345 - 2⁸ = 21365089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21365347) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12545 + ... + 14145.

It is an arithmetic number, because the mean of its divisors is an integer number (1708533).

Almost surely, 2^21365345 is an apocalyptic number.

21365345 is the 2669-th octagonal number.

It is an amenable number.

21365345 is a deficient number, since it is larger than the sum of its proper divisors (5971183).

21365345 is a wasteful number, since it uses less digits than its factorization.

21365345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1780.

The product of its digits is 10800, while the sum is 29.

The square root of 21365345 is about 4622.2662190748. The cubic root of 21365345 is about 277.4831632238.

The spelling of 21365345 in words is "twenty-one million, three hundred sixty-five thousand, three hundred forty-five".