21904191 has 12 divisors (see below), whose sum is σ = 31711680. Its totient is φ = 14569440.

The previous prime is 21904159. The next prime is 21904199. The reversal of 21904191 is 19140912.

It is not a de Polignac number, because 21904191 - 2⁵ = 21904159 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21904199) 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, 1771 + ... + 6851.

It is an arithmetic number, because the mean of its divisors is an integer number (2642640).

Almost surely, 2^21904191 is an apocalyptic number.

21904191 is a deficient number, since it is larger than the sum of its proper divisors (9807489).

21904191 is a wasteful number, since it uses less digits than its factorization.

21904191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5566 (or 5563 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 21904191 is about 4680.1913422423. The cubic root of 21904191 is about 279.7965826973.

The spelling of 21904191 in words is "twenty-one million, nine hundred four thousand, one hundred ninety-one".