261776721057 has 16 divisors (see below), whose sum is σ = 351666981120. Its totient is φ = 173202997392.

The previous prime is 261776721029. The next prime is 261776721119. The reversal of 261776721057 is 750127677162.

It is not a de Polignac number, because 261776721057 - 2¹⁶ = 261776655521 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261776721757) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1129638 + ... + 1341504.

It is an arithmetic number, because the mean of its divisors is an integer number (21979186320).

Almost surely, 2^261776721057 is an apocalyptic number.

It is an amenable number.

261776721057 is a deficient number, since it is larger than the sum of its proper divisors (89890260063).

261776721057 is a wasteful number, since it uses less digits than its factorization.

261776721057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214972.

The product of its (nonzero) digits is 1728720, while the sum is 51.

The spelling of 261776721057 in words is "two hundred sixty-one billion, seven hundred seventy-six million, seven hundred twenty-one thousand, fifty-seven".