21961878 has 24 divisors (see below), whose sum is σ = 44905272. Its totient is φ = 7160544.

The previous prime is 21961873. The next prime is 21961879. The reversal of 21961878 is 87816912.

21961878 is a nontrivial binomial coefficient, being equal to C(6628, 2).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21961873) 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 11 ways as a sum of consecutive naturals, for example, 12426 + ... + 14082.

It is an arithmetic number, because the mean of its divisors is an integer number (1871053).

Almost surely, 2^21961878 is an apocalyptic number.

21961878 is the 6627-th triangular number and also the 3314-th hexagonal number.

21961878 is an abundant number, since it is smaller than the sum of its proper divisors (22943394).

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

21961878 is a wasteful number, since it uses less digits than its factorization.

21961878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1756 (or 1709 counting only the distinct ones).

The product of its digits is 48384, while the sum is 42.

The square root of 21961878 is about 4686.3501789772. The cubic root of 21961878 is about 280.0419920014.

The spelling of 21961878 in words is "twenty-one million, nine hundred sixty-one thousand, eight hundred seventy-eight".