21907189 has 2 divisors, whose sum is σ = 21907190. Its totient is φ = 21907188.

The previous prime is 21907187. The next prime is 21907229. The reversal of 21907189 is 98170912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 1340964 = 4535^2 + 1158^2 .

It is a cyclic number.

It is not a de Polignac number, because 21907189 - 2¹ = 21907187 is a prime.

Together with 21907187, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21907187) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953594 + 10953595.

It is an arithmetic number, because the mean of its divisors is an integer number (10953595).

Almost surely, 2^21907189 is an apocalyptic number.

It is an amenable number.

21907189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21907189 is an equidigital number, since it uses as much as digits as its factorization.

21907189 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21907189 is about 4680.5116173342. The cubic root of 21907189 is about 279.8093472543.

The spelling of 21907189 in words is "twenty-one million, nine hundred seven thousand, one hundred eighty-nine".