1225556779 has 4 divisors (see below), whose sum is σ = 1229193784. Its totient is φ = 1221919776.

The previous prime is 1225556749. The next prime is 1225556851. The reversal of 1225556779 is 9776555221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9776555221 = 9661 ⋅1011961.

It is a cyclic number.

It is not a de Polignac number, because 1225556779 - 2¹¹ = 1225554731 is a prime.

It is a Duffinian number.

It is a plaindrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (1225556719) 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, 1817997 + ... + 1818670.

It is an arithmetic number, because the mean of its divisors is an integer number (307298446).

Almost surely, 2^1225556779 is an apocalyptic number.

1225556779 is a deficient number, since it is larger than the sum of its proper divisors (3637005).

1225556779 is an equidigital number, since it uses as much as digits as its factorization.

1225556779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3637004.

The product of its digits is 1323000, while the sum is 49.

The square root of 1225556779 is about 35007.9530821212. The cubic root of 1225556779 is about 1070.1495639185.

The spelling of 1225556779 in words is "one billion, two hundred twenty-five million, five hundred fifty-six thousand, seven hundred seventy-nine".