261309157 has 4 divisors (see below), whose sum is σ = 262753036. Its totient is φ = 259865280.

The previous prime is 261309127. The next prime is 261309163. The reversal of 261309157 is 751903162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 751903162 = 2 ⋅375951581.

It can be written as a sum of positive squares in 2 ways, for example, as 136562596 + 124746561 = 11686^2 + 11169^2 .

It is a cyclic number.

It is not a de Polignac number, because 261309157 - 2⁷ = 261309029 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 (261309107) 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, 721668 + ... + 722029.

It is an arithmetic number, because the mean of its divisors is an integer number (65688259).

Almost surely, 2^261309157 is an apocalyptic number.

It is an amenable number.

261309157 is a deficient number, since it is larger than the sum of its proper divisors (1443879).

261309157 is a wasteful number, since it uses less digits than its factorization.

261309157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1443878.

The product of its (nonzero) digits is 11340, while the sum is 34.

The square root of 261309157 is about 16165.0597586276. The cubic root of 261309157 is about 639.3198805295.

The spelling of 261309157 in words is "two hundred sixty-one million, three hundred nine thousand, one hundred fifty-seven".