261650639 has 2 divisors, whose sum is σ = 261650640. Its totient is φ = 261650638.

The previous prime is 261650603. The next prime is 261650659. The reversal of 261650639 is 936056162.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261650639 is a prime.

It is a super-2 number, since 2×261650639² = 136922113778216642, which contains 22 as substring.

It is a Sophie Germain prime.

It is a zygodrome in base 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261650659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130825319 + 130825320.

It is an arithmetic number, because the mean of its divisors is an integer number (130825320).

Almost surely, 2^261650639 is an apocalyptic number.

261650639 is a deficient number, since it is larger than the sum of its proper divisors (1).

261650639 is an equidigital number, since it uses as much as digits as its factorization.

261650639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 58320, while the sum is 38.

The square root of 261650639 is about 16175.6186589571. The cubic root of 261650639 is about 639.5982496504.

The spelling of 261650639 in words is "two hundred sixty-one million, six hundred fifty thousand, six hundred thirty-nine".