21917191 has 4 divisors (see below), whose sum is σ = 21975400. Its totient is φ = 21858984.

The previous prime is 21917177. The next prime is 21917201. The reversal of 21917191 is 19171912.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21917191 - 2¹¹ = 21915143 is a prime.

It is a super-2 number, since 2×21917191² = 960726522660962, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21917171) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 28536 + ... + 29293.

It is an arithmetic number, because the mean of its divisors is an integer number (5493850).

Almost surely, 2^21917191 is an apocalyptic number.

21917191 is a deficient number, since it is larger than the sum of its proper divisors (58209).

21917191 is an equidigital number, since it uses as much as digits as its factorization.

21917191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58208.

The product of its digits is 1134, while the sum is 31.

The square root of 21917191 is about 4681.5799683440. The cubic root of 21917191 is about 279.8519242562.

The spelling of 21917191 in words is "twenty-one million, nine hundred seventeen thousand, one hundred ninety-one".