1556121666 has 32 divisors (see below), whose sum is σ = 3398443776. Its totient is φ = 471098000.

The previous prime is 1556121661. The next prime is 1556121689. The reversal of 1556121666 is 6661216551.

It is not an unprimeable number, because it can be changed into a prime (1556121661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 61201 + ... + 82811.

It is an arithmetic number, because the mean of its divisors is an integer number (106201368).

Almost surely, 2^1556121666 is an apocalyptic number.

1556121666 is an abundant number, since it is smaller than the sum of its proper divisors (1842322110).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1556121666 is a wasteful number, since it uses less digits than its factorization.

1556121666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22718.

The product of its digits is 64800, while the sum is 39.

The square root of 1556121666 is about 39447.7079942549. The cubic root of 1556121666 is about 1158.8160894614.

The spelling of 1556121666 in words is "one billion, five hundred fifty-six million, one hundred twenty-one thousand, six hundred sixty-six".