21655765 has 8 divisors (see below), whose sum is σ = 27116928. Its totient is φ = 16571280.

The previous prime is 21655759. The next prime is 21655787. The reversal of 21655765 is 56755612.

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

It is not a de Polignac number, because 21655765 - 2¹³ = 21647573 is a prime.

It is a Duffinian number.

It is a zygodrome in base 9.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 94041 + ... + 94270.

It is an arithmetic number, because the mean of its divisors is an integer number (3389616).

Almost surely, 2^21655765 is an apocalyptic number.

It is an amenable number.

21655765 is a deficient number, since it is larger than the sum of its proper divisors (5461163).

21655765 is a wasteful number, since it uses less digits than its factorization.

21655765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188339.

The product of its digits is 63000, while the sum is 37.

The square root of 21655765 is about 4653.5755070698. The cubic root of 21655765 is about 278.7347890645.

The spelling of 21655765 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred sixty-five".