253721561 has 2 divisors, whose sum is σ = 253721562. Its totient is φ = 253721560.

The previous prime is 253721537. The next prime is 253721569. The reversal of 253721561 is 165127352.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 142945936 + 110775625 = 11956^2 + 10525^2 .

It is a cyclic number.

It is not a de Polignac number, because 253721561 - 2²⁶ = 186612697 is a prime.

It is not a weakly prime, because it can be changed into another prime (253721569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 126860780 + 126860781.

It is an arithmetic number, because the mean of its divisors is an integer number (126860781).

Almost surely, 2^253721561 is an apocalyptic number.

It is an amenable number.

253721561 is a deficient number, since it is larger than the sum of its proper divisors (1).

253721561 is an equidigital number, since it uses as much as digits as its factorization.

253721561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12600, while the sum is 32.

The square root of 253721561 is about 15928.6396468751. The cubic root of 253721561 is about 633.0710562819.

The spelling of 253721561 in words is "two hundred fifty-three million, seven hundred twenty-one thousand, five hundred sixty-one".