261338220157 has 4 divisors (see below), whose sum is σ = 298672251616. Its totient is φ = 224004188700.

The previous prime is 261338220139. The next prime is 261338220167. The reversal of 261338220157 is 751022833162.

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 261338220157 - 2¹⁵ = 261338187389 is a prime.

It is a super-2 number, since 2×261338220157² (a number of 24 digits) contains 22 as substring.

It is the 511213-rd Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261338220167) by changing a digit.

It is a nontrivial repunit in base 511212.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18667015719 + ... + 18667015732.

It is an arithmetic number, because the mean of its divisors is an integer number (74668062904).

Almost surely, 2^261338220157 is an apocalyptic number.

It is an amenable number.

261338220157 is a deficient number, since it is larger than the sum of its proper divisors (37334031459).

261338220157 is an equidigital number, since it uses as much as digits as its factorization.

261338220157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37334031458.

The product of its (nonzero) digits is 120960, while the sum is 40.

The spelling of 261338220157 in words is "two hundred sixty-one billion, three hundred thirty-eight million, two hundred twenty thousand, one hundred fifty-seven".