21919191 has 32 divisors (see below), whose sum is σ = 34569216. Its totient is φ = 12096000.

The previous prime is 21919189. The next prime is 21919213. The reversal of 21919191 is 19191912.

It is not a de Polignac number, because 21919191 - 2¹ = 21919189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21919111) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 90831 + ... + 91071.

It is an arithmetic number, because the mean of its divisors is an integer number (1080288).

Almost surely, 2^21919191 is an apocalyptic number.

21919191 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21919191 is a deficient number, since it is larger than the sum of its proper divisors (12650025).

21919191 is a wasteful number, since it uses less digits than its factorization.

21919191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383.

The product of its digits is 1458, while the sum is 33.

The square root of 21919191 is about 4681.7935665725. The cubic root of 21919191 is about 279.8604363997.

The spelling of 21919191 in words is "twenty-one million, nine hundred nineteen thousand, one hundred ninety-one".