1221279163225 has 81 divisors (see below), whose sum is σ = 1694335095327. Its totient is φ = 872598804000.

The previous prime is 1221279163211. The next prime is 1221279163253. The reversal of 1221279163225 is 5223619721221.

The square root of 1221279163225 is 1105115.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 439660498761 + 781618664464 = 663069^2 + 884092^2 .

It is not a de Polignac number, because 1221279163225 - 2⁵ = 1221279163193 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 4315473934 + ... + 4315474216.

Almost surely, 2^{1221279163225} is an apocalyptic number.

1221279163225 is the 1105115-th square number.

1221279163225 is the 552558-th centered octagonal number.

It is an amenable number.

1221279163225 is a deficient number, since it is larger than the sum of its proper divisors (473055932102).

1221279163225 is an frugal number, since it uses more digits than its factorization.

1221279163225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 740 (or 370 counting only the distinct ones).

The product of its digits is 181440, while the sum is 43.

The spelling of 1221279163225 in words is "one trillion, two hundred twenty-one billion, two hundred seventy-nine million, one hundred sixty-three thousand, two hundred twenty-five".