21722878 has 16 divisors (see below), whose sum is σ = 33978240. Its totient is φ = 10404000.

The previous prime is 21722873. The next prime is 21722887. The reversal of 21722878 is 87822712.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4528 + ... + 7996.

It is an arithmetic number, because the mean of its divisors is an integer number (2123640).

Almost surely, 2^21722878 is an apocalyptic number.

21722878 is a deficient number, since it is larger than the sum of its proper divisors (12255362).

21722878 is a wasteful number, since it uses less digits than its factorization.

21722878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3603.

The product of its digits is 25088, while the sum is 37.

The square root of 21722878 is about 4660.7808358686. The cubic root of 21722878 is about 279.0224328173.

It can be divided in two parts, 2172 and 2878, that added together give a triangular number (5050 = T₁₀₀).

The spelling of 21722878 in words is "twenty-one million, seven hundred twenty-two thousand, eight hundred seventy-eight".