1243721617 has 4 divisors (see below), whose sum is σ = 1251958336. Its totient is φ = 1235484900.

The previous prime is 1243721599. The next prime is 1243721623. The reversal of 1243721617 is 7161273421.

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, and also an emirpimes, since its reverse is a distinct semiprime: 7161273421 = 75743 ⋅94547.

It is a cyclic number.

It is not a de Polignac number, because 1243721617 - 2⁷ = 1243721489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1243721117) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4118133 + ... + 4118434.

It is an arithmetic number, because the mean of its divisors is an integer number (312989584).

Almost surely, 2^1243721617 is an apocalyptic number.

It is an amenable number.

1243721617 is a deficient number, since it is larger than the sum of its proper divisors (8236719).

1243721617 is an equidigital number, since it uses as much as digits as its factorization.

1243721617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8236718.

The product of its digits is 14112, while the sum is 34.

The square root of 1243721617 is about 35266.4375433641. The cubic root of 1243721617 is about 1075.4108015681.

The spelling of 1243721617 in words is "one billion, two hundred forty-three million, seven hundred twenty-one thousand, six hundred seventeen".