253665721 has 16 divisors (see below), whose sum is σ = 279002880. Its totient is φ = 229661440.

The previous prime is 253665719. The next prime is 253665739. The reversal of 253665721 is 127566352.

It is a cyclic number.

It is not a de Polignac number, because 253665721 - 2¹ = 253665719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (253665701) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44451 + ... + 49831.

It is an arithmetic number, because the mean of its divisors is an integer number (17437680).

Almost surely, 2^253665721 is an apocalyptic number.

It is an amenable number.

253665721 is a deficient number, since it is larger than the sum of its proper divisors (25337159).

253665721 is a wasteful number, since it uses less digits than its factorization.

253665721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5504.

The product of its digits is 75600, while the sum is 37.

The square root of 253665721 is about 15926.8867328176. The cubic root of 253665721 is about 633.0246099842.

The spelling of 253665721 in words is "two hundred fifty-three million, six hundred sixty-five thousand, seven hundred twenty-one".