21778249 has 8 divisors (see below), whose sum is σ = 22307328. Its totient is φ = 21252000.

The previous prime is 21778223. The next prime is 21778259. The reversal of 21778249 is 94287712.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21778249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21778219) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28624 + ... + 29374.

It is an arithmetic number, because the mean of its divisors is an integer number (2788416).

Almost surely, 2^21778249 is an apocalyptic number.

It is an amenable number.

21778249 is a deficient number, since it is larger than the sum of its proper divisors (529079).

21778249 is an equidigital number, since it uses as much as digits as its factorization.

21778249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1415.

The product of its digits is 56448, while the sum is 40.

The square root of 21778249 is about 4666.7171544888. The cubic root of 21778249 is about 279.2593050938.

The spelling of 21778249 in words is "twenty-one million, seven hundred seventy-eight thousand, two hundred forty-nine".