261553181 has 2 divisors, whose sum is σ = 261553182. Its totient is φ = 261553180.

The previous prime is 261553151. The next prime is 261553207. The reversal of 261553181 is 181355162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 195049156 + 66504025 = 13966^2 + 8155^2 .

It is a cyclic number.

It is not a de Polignac number, because 261553181 - 2¹⁴ = 261536797 is a prime.

It is a super-2 number, since 2×261553181² = 136820132982437522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261553151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130776590 + 130776591.

It is an arithmetic number, because the mean of its divisors is an integer number (130776591).

Almost surely, 2^261553181 is an apocalyptic number.

It is an amenable number.

261553181 is a deficient number, since it is larger than the sum of its proper divisors (1).

261553181 is an equidigital number, since it uses as much as digits as its factorization.

261553181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7200, while the sum is 32.

The square root of 261553181 is about 16172.6058815517. The cubic root of 261553181 is about 639.5188285983.

The spelling of 261553181 in words is "two hundred sixty-one million, five hundred fifty-three thousand, one hundred eighty-one".