21778572 has 24 divisors (see below), whose sum is σ = 51105600. Its totient is φ = 7218256.

The previous prime is 21778543. The next prime is 21778573. The reversal of 21778572 is 27587712.

It is a self number, because there is not a number n which added to its sum of digits gives 21778572.

It is not an unprimeable number, because it can be changed into a prime (21778573) 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, 2922 + ... + 7217.

It is an arithmetic number, because the mean of its divisors is an integer number (2129400).

Almost surely, 2^21778572 is an apocalyptic number.

It is an amenable number.

21778572 is an abundant number, since it is smaller than the sum of its proper divisors (29327028).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21778572 is a wasteful number, since it uses less digits than its factorization.

21778572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10325 (or 10323 counting only the distinct ones).

The product of its digits is 54880, while the sum is 39.

The square root of 21778572 is about 4666.7517611289. The cubic root of 21778572 is about 279.2606856809.

The spelling of 21778572 in words is "twenty-one million, seven hundred seventy-eight thousand, five hundred seventy-two".