261161999 has 4 divisors (see below), whose sum is σ = 298470864. Its totient is φ = 223853136.

The previous prime is 261161977. The next prime is 261162017. The reversal of 261161999 is 999161162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261161999 - 2¹² = 261157903 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261161969) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18654422 + ... + 18654435.

It is an arithmetic number, because the mean of its divisors is an integer number (74617716).

Almost surely, 2^261161999 is an apocalyptic number.

261161999 is a deficient number, since it is larger than the sum of its proper divisors (37308865).

261161999 is an equidigital number, since it uses as much as digits as its factorization.

261161999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37308864.

The product of its digits is 52488, while the sum is 44.

The square root of 261161999 is about 16160.5073868366. The cubic root of 261161999 is about 639.1998455712.

The spelling of 261161999 in words is "two hundred sixty-one million, one hundred sixty-one thousand, nine hundred ninety-nine".