1217921257 has 4 divisors (see below), whose sum is σ = 1391910016. Its totient is φ = 1043932500.

The previous prime is 1217921251. The next prime is 1217921311. The reversal of 1217921257 is 7521297121.

It is a happy number.

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 1217921257 - 2³ = 1217921249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1217921251) 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, 86994369 + ... + 86994382.

It is an arithmetic number, because the mean of its divisors is an integer number (347977504).

Almost surely, 2^1217921257 is an apocalyptic number.

It is an amenable number.

1217921257 is a deficient number, since it is larger than the sum of its proper divisors (173988759).

1217921257 is an equidigital number, since it uses as much as digits as its factorization.

1217921257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173988758.

The product of its digits is 17640, while the sum is 37.

The square root of 1217921257 is about 34898.7285871563. The cubic root of 1217921257 is about 1067.9225002445.

The spelling of 1217921257 in words is "one billion, two hundred seventeen million, nine hundred twenty-one thousand, two hundred fifty-seven".