21885817 has 4 divisors (see below), whose sum is σ = 23173236. Its totient is φ = 20598400.

The previous prime is 21885803. The next prime is 21885827. The reversal of 21885817 is 71858812.

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 18844281 + 3041536 = 4341^2 + 1744^2 .

It is a cyclic number.

It is not a de Polignac number, because 21885817 - 2¹⁵ = 21853049 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 21885817.

It is not an unprimeable number, because it can be changed into a prime (21885827) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 643684 + ... + 643717.

It is an arithmetic number, because the mean of its divisors is an integer number (5793309).

Almost surely, 2^21885817 is an apocalyptic number.

It is an amenable number.

21885817 is a deficient number, since it is larger than the sum of its proper divisors (1287419).

21885817 is a wasteful number, since it uses less digits than its factorization.

21885817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1287418.

The product of its digits is 35840, while the sum is 40.

The square root of 21885817 is about 4678.2279764885. The cubic root of 21885817 is about 279.7183264318.

The spelling of 21885817 in words is "twenty-one million, eight hundred eighty-five thousand, eight hundred seventeen".