1561666860 has 72 divisors (see below), whose sum is σ = 5101452720. Its totient is φ = 384409728.

The previous prime is 1561666859. The next prime is 1561666861. The reversal of 1561666860 is 686661651.

It is an interprime number because it is at equal distance from previous prime (1561666859) and next prime (1561666861).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (1561666861) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 331350 + ... + 336029.

It is an arithmetic number, because the mean of its divisors is an integer number (70853510).

Almost surely, 2^1561666860 is an apocalyptic number.

1561666860 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561666860 is an abundant number, since it is smaller than the sum of its proper divisors (3539785860).

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

1561666860 is a wasteful number, since it uses less digits than its factorization.

1561666860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 667407 (or 667402 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 1561666860 is about 39517.9308668862. The cubic root of 1561666860 is about 1160.1909267580.

The spelling of 1561666860 in words is "one billion, five hundred sixty-one million, six hundred sixty-six thousand, eight hundred sixty".