21878199 has 24 divisors (see below), whose sum is σ = 36714912. Its totient is φ = 12294720.

The previous prime is 21878149. The next prime is 21878243. The reversal of 21878199 is 99187812.

It is not a de Polignac number, because 21878199 - 2⁷ = 21878071 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878149) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 997 + ... + 6689.

It is an arithmetic number, because the mean of its divisors is an integer number (1529788).

Almost surely, 2^21878199 is an apocalyptic number.

21878199 is a deficient number, since it is larger than the sum of its proper divisors (14836713).

21878199 is a wasteful number, since it uses less digits than its factorization.

21878199 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5767 (or 5764 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 21878199 is about 4677.4137084504. The cubic root of 21878199 is about 279.6858679451.

The spelling of 21878199 in words is "twenty-one million, eight hundred seventy-eight thousand, one hundred ninety-nine".