261771772641 has 4 divisors (see below), whose sum is σ = 349029030192. Its totient is φ = 174514515092.

The previous prime is 261771772583. The next prime is 261771772667. The reversal of 261771772641 is 146277177162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 261771772641 - 2²² = 261767578337 is a prime.

It is a super-2 number, since 2×261771772641² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261771772841) 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, 43628628771 + ... + 43628628776.

It is an arithmetic number, because the mean of its divisors is an integer number (87257257548).

Almost surely, 2^261771772641 is an apocalyptic number.

It is an amenable number.

261771772641 is a deficient number, since it is larger than the sum of its proper divisors (87257257551).

261771772641 is an equidigital number, since it uses as much as digits as its factorization.

261771772641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87257257550.

The product of its digits is 1382976, while the sum is 51.

The spelling of 261771772641 in words is "two hundred sixty-one billion, seven hundred seventy-one million, seven hundred seventy-two thousand, six hundred forty-one".