21440291 has 2 divisors, whose sum is σ = 21440292. Its totient is φ = 21440290.

The previous prime is 21440269. The next prime is 21440317. The reversal of 21440291 is 19204412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21440291 - 2¹⁴ = 21423907 is a prime.

It is not a weakly prime, because it can be changed into another prime (21440261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10720145 + 10720146.

It is an arithmetic number, because the mean of its divisors is an integer number (10720146).

Almost surely, 2^21440291 is an apocalyptic number.

21440291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21440291 is an equidigital number, since it uses as much as digits as its factorization.

21440291 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21440291 is about 4630.3661842234. The cubic root of 21440291 is about 277.8072391804.

The spelling of 21440291 in words is "twenty-one million, four hundred forty thousand, two hundred ninety-one".