21353765 has 8 divisors (see below), whose sum is σ = 25716768. Its totient is φ = 17021520.

The previous prime is 21353737. The next prime is 21353767. The reversal of 21353765 is 56735312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21353765 - 2²⁰ = 20305189 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21353767) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6131 + ... + 8960.

It is an arithmetic number, because the mean of its divisors is an integer number (3214596).

Almost surely, 2^21353765 is an apocalyptic number.

It is an amenable number.

21353765 is a deficient number, since it is larger than the sum of its proper divisors (4363003).

21353765 is a wasteful number, since it uses less digits than its factorization.

21353765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15379.

The product of its digits is 18900, while the sum is 32.

The square root of 21353765 is about 4621.0134169898. The cubic root of 21353765 is about 277.4330222793.

The spelling of 21353765 in words is "twenty-one million, three hundred fifty-three thousand, seven hundred sixty-five".