1253689721 has 4 divisors (see below), whose sum is σ = 1259311872. Its totient is φ = 1248067572.

The previous prime is 1253689637. The next prime is 1253689739. The reversal of 1253689721 is 1279863521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1253689721 - 2¹⁰ = 1253688697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1253689621) 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 in 3 ways as a sum of consecutive naturals, for example, 2810741 + ... + 2811186.

It is an arithmetic number, because the mean of its divisors is an integer number (314827968).

Almost surely, 2^1253689721 is an apocalyptic number.

It is an amenable number.

1253689721 is a deficient number, since it is larger than the sum of its proper divisors (5622151).

1253689721 is an equidigital number, since it uses as much as digits as its factorization.

1253689721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5622150.

The product of its digits is 181440, while the sum is 44.

The square root of 1253689721 is about 35407.4811445265. The cubic root of 1253689721 is about 1078.2762055808.

The spelling of 1253689721 in words is "one billion, two hundred fifty-three million, six hundred eighty-nine thousand, seven hundred twenty-one".