21608291 has 2 divisors, whose sum is σ = 21608292. Its totient is φ = 21608290.

The previous prime is 21608281. The next prime is 21608311. The reversal of 21608291 is 19280612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21608291 - 2⁶ = 21608227 is a prime.

It is not a weakly prime, because it can be changed into another prime (21608281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804145 + 10804146.

It is an arithmetic number, because the mean of its divisors is an integer number (10804146).

Almost surely, 2^21608291 is an apocalyptic number.

21608291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21608291 is an equidigital number, since it uses as much as digits as its factorization.

21608291 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21608291 is about 4648.4718994526. The cubic root of 21608291 is about 278.5309582484.

The spelling of 21608291 in words is "twenty-one million, six hundred eight thousand, two hundred ninety-one".