21995923 has 4 divisors (see below), whose sum is σ = 22009680. Its totient is φ = 21982168.

The previous prime is 21995921. The next prime is 21995951. The reversal of 21995923 is 32959912.

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

It is a cyclic number.

It is not a de Polignac number, because 21995923 - 2¹ = 21995921 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21995921) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 4108 + ... + 7801.

It is an arithmetic number, because the mean of its divisors is an integer number (5502420).

Almost surely, 2^21995923 is an apocalyptic number.

21995923 is a deficient number, since it is larger than the sum of its proper divisors (13757).

21995923 is a wasteful number, since it uses less digits than its factorization.

21995923 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13756.

The product of its digits is 43740, while the sum is 40.

The square root of 21995923 is about 4689.9811300260. The cubic root of 21995923 is about 280.1866230351.

The spelling of 21995923 in words is "twenty-one million, nine hundred ninety-five thousand, nine hundred twenty-three".