21913805 has 8 divisors (see below), whose sum is σ = 27007512. Its totient is φ = 17057088.

The previous prime is 21913769. The next prime is 21913817. The reversal of 21913805 is 50831912.

It can be written as a sum of positive squares in 4 ways, for example, as 1247689 + 20666116 = 1117^2 + 4546^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21913805 - 2⁶ = 21913741 is a prime.

It is a Duffinian number.

It is a Curzon number.

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, 59042 + ... + 59411.

It is an arithmetic number, because the mean of its divisors is an integer number (3375939).

Almost surely, 2^21913805 is an apocalyptic number.

It is an amenable number.

21913805 is a deficient number, since it is larger than the sum of its proper divisors (5093707).

21913805 is a wasteful number, since it uses less digits than its factorization.

21913805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118495.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 21913805 is about 4681.2183243254. The cubic root of 21913805 is about 279.8375120167.

The spelling of 21913805 in words is "twenty-one million, nine hundred thirteen thousand, eight hundred five".