21645793 has 4 divisors (see below), whose sum is σ = 23310868. Its totient is φ = 19980720.

The previous prime is 21645791. The next prime is 21645797. The reversal of 21645793 is 39754612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14500864 + 7144929 = 3808^2 + 2673^2 .

It is a cyclic number.

It is not a de Polignac number, because 21645793 - 2¹ = 21645791 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21645791) 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 3 ways as a sum of consecutive naturals, for example, 832518 + ... + 832543.

It is an arithmetic number, because the mean of its divisors is an integer number (5827717).

Almost surely, 2^21645793 is an apocalyptic number.

It is an amenable number.

21645793 is a deficient number, since it is larger than the sum of its proper divisors (1665075).

21645793 is a wasteful number, since it uses less digits than its factorization.

21645793 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1665074.

The product of its digits is 45360, while the sum is 37.

The square root of 21645793 is about 4652.5039494878. The cubic root of 21645793 is about 278.6919987642.

The spelling of 21645793 in words is "twenty-one million, six hundred forty-five thousand, seven hundred ninety-three".