261156557 has 4 divisors (see below), whose sum is σ = 261614496. Its totient is φ = 260698620.

The previous prime is 261156529. The next prime is 261156563. The reversal of 261156557 is 755651162.

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 261156557 - 2²² = 256962253 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261156557.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261156457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 228113 + ... + 229254.

It is an arithmetic number, because the mean of its divisors is an integer number (65403624).

Almost surely, 2^261156557 is an apocalyptic number.

It is an amenable number.

261156557 is a deficient number, since it is larger than the sum of its proper divisors (457939).

261156557 is an equidigital number, since it uses as much as digits as its factorization.

261156557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457938.

The product of its digits is 63000, while the sum is 38.

The square root of 261156557 is about 16160.3390125331. The cubic root of 261156557 is about 639.1954057347.

The spelling of 261156557 in words is "two hundred sixty-one million, one hundred fifty-six thousand, five hundred fifty-seven".