261007991 has 2 divisors, whose sum is σ = 261007992. Its totient is φ = 261007990.

The previous prime is 261007969. The next prime is 261008039. The reversal of 261007991 is 199700162.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261007991 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261007931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130503995 + 130503996.

It is an arithmetic number, because the mean of its divisors is an integer number (130503996).

Almost surely, 2^261007991 is an apocalyptic number.

261007991 is a deficient number, since it is larger than the sum of its proper divisors (1).

261007991 is an equidigital number, since it uses as much as digits as its factorization.

261007991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 261007991 is about 16155.7417347518. The cubic root of 261007991 is about 639.0741748546.

The spelling of 261007991 in words is "two hundred sixty-one million, seven thousand, nine hundred ninety-one".