21742765 has 8 divisors (see below), whose sum is σ = 28463328. Its totient is φ = 15812880.

The previous prime is 21742757. The next prime is 21742771. The reversal of 21742765 is 56724712.

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

It is not a de Polignac number, because 21742765 - 2³ = 21742757 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21742765.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 197607 + ... + 197716.

It is an arithmetic number, because the mean of its divisors is an integer number (3557916).

Almost surely, 2^21742765 is an apocalyptic number.

It is an amenable number.

21742765 is a deficient number, since it is larger than the sum of its proper divisors (6720563).

21742765 is a wasteful number, since it uses less digits than its factorization.

21742765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 395339.

The product of its digits is 23520, while the sum is 34.

The square root of 21742765 is about 4662.9137886090. The cubic root of 21742765 is about 279.1075539303.

The spelling of 21742765 in words is "twenty-one million, seven hundred forty-two thousand, seven hundred sixty-five".