21768413 has 4 divisors (see below), whose sum is σ = 21813600. Its totient is φ = 21723228.

The previous prime is 21768407. The next prime is 21768431. The reversal of 21768413 is 31486712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21768413 - 2⁶ = 21768349 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 21768413.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21768113) 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, 21863 + ... + 22836.

It is an arithmetic number, because the mean of its divisors is an integer number (5453400).

Almost surely, 2^21768413 is an apocalyptic number.

It is an amenable number.

21768413 is a deficient number, since it is larger than the sum of its proper divisors (45187).

21768413 is an equidigital number, since it uses as much as digits as its factorization.

21768413 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45186.

The product of its digits is 8064, while the sum is 32.

The square root of 21768413 is about 4665.6631897298. The cubic root of 21768413 is about 279.2172568992.

The spelling of 21768413 in words is "twenty-one million, seven hundred sixty-eight thousand, four hundred thirteen".