253721681 has 2 divisors, whose sum is σ = 253721682. Its totient is φ = 253721680.

The previous prime is 253721659. The next prime is 253721707. The reversal of 253721681 is 186127352.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 207821056 + 45900625 = 14416^2 + 6775^2 .

It is a cyclic number.

It is not a de Polignac number, because 253721681 - 2¹⁰ = 253720657 is a prime.

It is a super-2 number, since 2×253721681² = 128749382818931522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (253721641) 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, 126860840 + 126860841.

It is an arithmetic number, because the mean of its divisors is an integer number (126860841).

Almost surely, 2^253721681 is an apocalyptic number.

It is an amenable number.

253721681 is a deficient number, since it is larger than the sum of its proper divisors (1).

253721681 is an equidigital number, since it uses as much as digits as its factorization.

253721681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20160, while the sum is 35.

The square root of 253721681 is about 15928.6434136746. The cubic root of 253721681 is about 633.0711560875.

The spelling of 253721681 in words is "two hundred fifty-three million, seven hundred twenty-one thousand, six hundred eighty-one".