1251221779 has 2 divisors, whose sum is σ = 1251221780. Its totient is φ = 1251221778.

The previous prime is 1251221773. The next prime is 1251221809. The reversal of 1251221779 is 9771221521.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1251221779 - 2⁷ = 1251221651 is a prime.

It is not a weakly prime, because it can be changed into another prime (1251221773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 625610889 + 625610890.

It is an arithmetic number, because the mean of its divisors is an integer number (625610890).

Almost surely, 2^1251221779 is an apocalyptic number.

1251221779 is a deficient number, since it is larger than the sum of its proper divisors (1).

1251221779 is an equidigital number, since it uses as much as digits as its factorization.

1251221779 is an odious number, because the sum of its binary digits is odd.

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

The square root of 1251221779 is about 35372.6134035923. The cubic root of 1251221779 is about 1077.5681964721.

The spelling of 1251221779 in words is "one billion, two hundred fifty-one million, two hundred twenty-one thousand, seven hundred seventy-nine".