291023261 has 2 divisors, whose sum is σ = 291023262. Its totient is φ = 291023260.

The previous prime is 291023231. The next prime is 291023263. The reversal of 291023261 is 162320192.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 207648100 + 83375161 = 14410^2 + 9131^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-291023261 is a prime.

It is a Sophie Germain prime.

Together with 291023263, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 291023261.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (291023263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 145511630 + 145511631.

It is an arithmetic number, because the mean of its divisors is an integer number (145511631).

Almost surely, 2^291023261 is an apocalyptic number.

It is an amenable number.

291023261 is a deficient number, since it is larger than the sum of its proper divisors (1).

291023261 is an equidigital number, since it uses as much as digits as its factorization.

291023261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 291023261 is about 17059.4038875923. The cubic root of 291023261 is about 662.6881950692.

The spelling of 291023261 in words is "two hundred ninety-one million, twenty-three thousand, two hundred sixty-one".