21873978 has 48 divisors (see below), whose sum is σ = 57021120. Its totient is φ = 5920128.

The previous prime is 21873977. The next prime is 21874009. The reversal of 21873978 is 87937812.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21873977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2175 + ... + 6962.

It is an arithmetic number, because the mean of its divisors is an integer number (1187940).

Almost surely, 2^21873978 is an apocalyptic number.

21873978 is an abundant number, since it is smaller than the sum of its proper divisors (35147142).

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

21873978 is a wasteful number, since it uses less digits than its factorization.

21873978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9171 (or 9168 counting only the distinct ones).

The product of its digits is 169344, while the sum is 45.

The square root of 21873978 is about 4676.9624757956. The cubic root of 21873978 is about 279.6678800236.

The spelling of 21873978 in words is "twenty-one million, eight hundred seventy-three thousand, nine hundred seventy-eight".