1556406121 has 2 divisors, whose sum is σ = 1556406122. Its totient is φ = 1556406120.

The previous prime is 1556406079. The next prime is 1556406127. The reversal of 1556406121 is 1216046551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1232010000 + 324396121 = 35100^2 + 18011^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1556406121 is a prime.

It is not a weakly prime, because it can be changed into another prime (1556406127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 778203060 + 778203061.

It is an arithmetic number, because the mean of its divisors is an integer number (778203061).

Almost surely, 2^1556406121 is an apocalyptic number.

It is an amenable number.

1556406121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1556406121 is an equidigital number, since it uses as much as digits as its factorization.

1556406121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7200, while the sum is 31.

The square root of 1556406121 is about 39451.3132987991. The cubic root of 1556406121 is about 1158.8866946835.

The spelling of 1556406121 in words is "one billion, five hundred fifty-six million, four hundred six thousand, one hundred twenty-one".