21213878 has 32 divisors (see below), whose sum is σ = 37635840. Its totient is φ = 8779680.

The previous prime is 21213859. The next prime is 21213893. The reversal of 21213878 is 87831212.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 78728 + ... + 78996.

It is an arithmetic number, because the mean of its divisors is an integer number (1176120).

Almost surely, 2^21213878 is an apocalyptic number.

21213878 is a deficient number, since it is larger than the sum of its proper divisors (16421962).

21213878 is a wasteful number, since it uses less digits than its factorization.

21213878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 452.

The product of its digits is 5376, while the sum is 32.

The square root of 21213878 is about 4605.8525812275. The cubic root of 21213878 is about 276.8258798767.

The spelling of 21213878 in words is "twenty-one million, two hundred thirteen thousand, eight hundred seventy-eight".