261661019 has 2 divisors, whose sum is σ = 261661020. Its totient is φ = 261661018.

The previous prime is 261660983. The next prime is 261661031. The reversal of 261661019 is 910166162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261661019 - 2²⁴ = 244883803 is a prime.

It is a super-2 number, since 2×261661019² = 136932977728236722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261661219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130830509 + 130830510.

It is an arithmetic number, because the mean of its divisors is an integer number (130830510).

Almost surely, 2^261661019 is an apocalyptic number.

261661019 is a deficient number, since it is larger than the sum of its proper divisors (1).

261661019 is an equidigital number, since it uses as much as digits as its factorization.

261661019 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 261661019 is about 16175.9395090363. The cubic root of 261661019 is about 639.6067074195.

The spelling of 261661019 in words is "two hundred sixty-one million, six hundred sixty-one thousand, nineteen".