21766878 has 144 divisors (see below), whose sum is σ = 60821280. Its totient is φ = 5588352.

The previous prime is 21766873. The next prime is 21766889. The reversal of 21766878 is 87866712.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21766873) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 588276 + ... + 588312.

It is an arithmetic number, because the mean of its divisors is an integer number (422370).

Almost surely, 2^21766878 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21766878, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30410640).

21766878 is an abundant number, since it is smaller than the sum of its proper divisors (39054402).

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

21766878 is a wasteful number, since it uses less digits than its factorization.

21766878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111 (or 101 counting only the distinct ones).

The product of its digits is 225792, while the sum is 45.

The square root of 21766878 is about 4665.4986871716. The cubic root of 21766878 is about 279.2106937418.

The spelling of 21766878 in words is "twenty-one million, seven hundred sixty-six thousand, eight hundred seventy-eight".