261664157 has 2 divisors, whose sum is σ = 261664158. Its totient is φ = 261664156.

The previous prime is 261664133. The next prime is 261664177. The reversal of 261664157 is 751466162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 260467321 + 1196836 = 16139^2 + 1094^2 .

It is a cyclic number.

It is not a de Polignac number, because 261664157 - 2⁶ = 261664093 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261664157.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261664177) 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 as a sum of consecutive naturals, namely, 130832078 + 130832079.

It is an arithmetic number, because the mean of its divisors is an integer number (130832079).

Almost surely, 2^261664157 is an apocalyptic number.

It is an amenable number.

261664157 is a deficient number, since it is larger than the sum of its proper divisors (1).

261664157 is an equidigital number, since it uses as much as digits as its factorization.

261664157 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 60480, while the sum is 38.

The square root of 261664157 is about 16176.0365046571. The cubic root of 261664157 is about 639.6092642617.

The spelling of 261664157 in words is "two hundred sixty-one million, six hundred sixty-four thousand, one hundred fifty-seven".