261603557 has 2 divisors, whose sum is σ = 261603558. Its totient is φ = 261603556.

The previous prime is 261603553. The next prime is 261603569. The reversal of 261603557 is 755306162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 165739876 + 95863681 = 12874^2 + 9791^2 .

It is a cyclic number.

It is not a de Polignac number, because 261603557 - 2² = 261603553 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261603553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130801778 + 130801779.

It is an arithmetic number, because the mean of its divisors is an integer number (130801779).

Almost surely, 2^261603557 is an apocalyptic number.

It is an amenable number.

261603557 is a deficient number, since it is larger than the sum of its proper divisors (1).

261603557 is an equidigital number, since it uses as much as digits as its factorization.

261603557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37800, while the sum is 35.

The square root of 261603557 is about 16174.1632550188. The cubic root of 261603557 is about 639.5598837702.

The spelling of 261603557 in words is "two hundred sixty-one million, six hundred three thousand, five hundred fifty-seven".