21878099 has 12 divisors (see below), whose sum is σ = 23841576. Its totient is φ = 19996032.

The previous prime is 21878089. The next prime is 21878111. The reversal of 21878099 is 99087812.

It is a de Polignac number, because none of the positive numbers 2^k-21878099 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878089) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 126377 + ... + 126549.

It is an arithmetic number, because the mean of its divisors is an integer number (1986798).

Almost surely, 2^21878099 is an apocalyptic number.

21878099 is a deficient number, since it is larger than the sum of its proper divisors (1963477).

21878099 is an equidigital number, since it uses as much as digits as its factorization.

21878099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406 (or 233 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 21878099 is about 4677.4030187701. The cubic root of 21878099 is about 279.6854418188.

The spelling of 21878099 in words is "twenty-one million, eight hundred seventy-eight thousand, ninety-nine".