261899247891 has 4 divisors (see below), whose sum is σ = 349198997192. Its totient is φ = 174599498592.

The previous prime is 261899247839. The next prime is 261899247899. The reversal of 261899247891 is 198742998162.

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

It is not a de Polignac number, because 261899247891 - 2¹¹ = 261899245843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261899247899) 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, 43649874646 + ... + 43649874651.

It is an arithmetic number, because the mean of its divisors is an integer number (87299749298).

Almost surely, 2^261899247891 is an apocalyptic number.

261899247891 is a deficient number, since it is larger than the sum of its proper divisors (87299749301).

261899247891 is an equidigital number, since it uses as much as digits as its factorization.

261899247891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87299749300.

The product of its digits is 31352832, while the sum is 66.

The spelling of 261899247891 in words is "two hundred sixty-one billion, eight hundred ninety-nine million, two hundred forty-seven thousand, eight hundred ninety-one".