261722481991 has 4 divisors (see below), whose sum is σ = 262896125632. Its totient is φ = 260548838352.

The previous prime is 261722481953. The next prime is 261722482019. The reversal of 261722481991 is 199184227162.

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 261722481991 - 2²³ = 261714093383 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 (261722481931) 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, 586821486 + ... + 586821931.

It is an arithmetic number, because the mean of its divisors is an integer number (65724031408).

Almost surely, 2^261722481991 is an apocalyptic number.

261722481991 is a deficient number, since it is larger than the sum of its proper divisors (1173643641).

261722481991 is a wasteful number, since it uses less digits than its factorization.

261722481991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1173643640.

The product of its digits is 870912, while the sum is 52.

The spelling of 261722481991 in words is "two hundred sixty-one billion, seven hundred twenty-two million, four hundred eighty-one thousand, nine hundred ninety-one".