1556226721 has 12 divisors (see below), whose sum is σ = 1811538432. Its totient is φ = 1332999528.

The previous prime is 1556226671. The next prime is 1556226761. The reversal of 1556226721 is 1276226551.

It is not a de Polignac number, because 1556226721 - 2⁷ = 1556226593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1556226761) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67536 + ... + 87598.

It is an arithmetic number, because the mean of its divisors is an integer number (150961536).

Almost surely, 2^1556226721 is an apocalyptic number.

It is an amenable number.

1556226721 is a deficient number, since it is larger than the sum of its proper divisors (255311711).

1556226721 is a wasteful number, since it uses less digits than its factorization.

1556226721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21660 (or 21653 counting only the distinct ones).

The product of its digits is 50400, while the sum is 37.

The square root of 1556226721 is about 39449.0395447088. The cubic root of 1556226721 is about 1158.8421664037.

The spelling of 1556226721 in words is "one billion, five hundred fifty-six million, two hundred twenty-six thousand, seven hundred twenty-one".