21778856 has 32 divisors (see below), whose sum is σ = 44733600. Its totient is φ = 9858240.

The previous prime is 21778843. The next prime is 21778859. The reversal of 21778856 is 65887712.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is not an unprimeable number, because it can be changed into a prime (21778859) 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, 33026 + ... + 33678.

It is an arithmetic number, because the mean of its divisors is an integer number (1397925).

Almost surely, 2^21778856 is an apocalyptic number.

21778856 is the 2495-th centered heptagonal number.

It is an amenable number.

21778856 is an abundant number, since it is smaller than the sum of its proper divisors (22954744).

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

21778856 is a wasteful number, since it uses less digits than its factorization.

21778856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1049 (or 1045 counting only the distinct ones).

The product of its digits is 188160, while the sum is 44.

The square root of 21778856 is about 4666.7821890463. The cubic root of 21778856 is about 279.2618995604.

It can be divided in two parts, 21 and 778856, that added together give a palindrome (778877).

The spelling of 21778856 in words is "twenty-one million, seven hundred seventy-eight thousand, eight hundred fifty-six".