261321553 has 2 divisors, whose sum is σ = 261321554. Its totient is φ = 261321552.

The previous prime is 261321547. The next prime is 261321559. The reversal of 261321553 is 355123162.

It is a balanced prime because it is at equal distance from previous prime (261321547) and next prime (261321559).

It can be written as a sum of positive squares in only one way, i.e., 150503824 + 110817729 = 12268^2 + 10527^2 .

It is a cyclic number.

It is not a de Polignac number, because 261321553 - 2¹⁷ = 261190481 is a prime.

It is not a weakly prime, because it can be changed into another prime (261321559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130660776 + 130660777.

It is an arithmetic number, because the mean of its divisors is an integer number (130660777).

Almost surely, 2^261321553 is an apocalyptic number.

It is an amenable number.

261321553 is a deficient number, since it is larger than the sum of its proper divisors (1).

261321553 is an equidigital number, since it uses as much as digits as its factorization.

261321553 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5400, while the sum is 28.

The square root of 261321553 is about 16165.4431736343. The cubic root of 261321553 is about 639.3299897350.

The spelling of 261321553 in words is "two hundred sixty-one million, three hundred twenty-one thousand, five hundred fifty-three".