21906289 has 2 divisors, whose sum is σ = 21906290. Its totient is φ = 21906288.

The previous prime is 21906263. The next prime is 21906301. The reversal of 21906289 is 98260912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11505664 + 10400625 = 3392^2 + 3225^2 .

It is a cyclic number.

It is not a de Polignac number, because 21906289 - 2⁷ = 21906161 is a prime.

It is not a weakly prime, because it can be changed into another prime (21906389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953144 + 10953145.

It is an arithmetic number, because the mean of its divisors is an integer number (10953145).

Almost surely, 2^21906289 is an apocalyptic number.

It is an amenable number.

21906289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906289 is an equidigital number, since it uses as much as digits as its factorization.

21906289 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 21906289 is about 4680.4154730109. The cubic root of 21906289 is about 279.8055154549.

The spelling of 21906289 in words is "twenty-one million, nine hundred six thousand, two hundred eighty-nine".