21901917 has 4 divisors (see below), whose sum is σ = 29202560. Its totient is φ = 14601276.

The previous prime is 21901909. The next prime is 21901969. The reversal of 21901917 is 71910912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21901917 - 2³ = 21901909 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 (21901907) 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, 3650317 + ... + 3650322.

It is an arithmetic number, because the mean of its divisors is an integer number (7300640).

Almost surely, 2^21901917 is an apocalyptic number.

It is an amenable number.

21901917 is a deficient number, since it is larger than the sum of its proper divisors (7300643).

21901917 is an equidigital number, since it uses as much as digits as its factorization.

21901917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7300642.

The product of its (nonzero) digits is 1134, while the sum is 30.

The square root of 21901917 is about 4679.9483971514. The cubic root of 21901917 is about 279.7868999315.

The spelling of 21901917 in words is "twenty-one million, nine hundred one thousand, nine hundred seventeen".