21369765 has 32 divisors (see below), whose sum is σ = 36481536. Its totient is φ = 10644480.

The previous prime is 21369749. The next prime is 21369767. The reversal of 21369765 is 56796312.

21369765 = T₄₁₄ + T₄₁₅ + ... + T₅₈₃.

It is not a de Polignac number, because 21369765 - 2⁴ = 21369749 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21369767) 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 31 ways as a sum of consecutive naturals, for example, 45924 + ... + 46386.

It is an arithmetic number, because the mean of its divisors is an integer number (1140048).

Almost surely, 2^21369765 is an apocalyptic number.

It is an amenable number.

21369765 is a deficient number, since it is larger than the sum of its proper divisors (15111771).

21369765 is a wasteful number, since it uses less digits than its factorization.

21369765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 669.

The product of its digits is 68040, while the sum is 39.

The square root of 21369765 is about 4622.7443147983. The cubic root of 21369765 is about 277.5022968725.

The spelling of 21369765 in words is "twenty-one million, three hundred sixty-nine thousand, seven hundred sixty-five".