1561666212 has 18 divisors (see below), whose sum is σ = 3947545238. Its totient is φ = 520555392.

The previous prime is 1561666207. The next prime is 1561666243. The reversal of 1561666212 is 2126661651.

It can be written as a sum of positive squares in only one way, i.e., 1282642596 + 279023616 = 35814^2 + 16704^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 43379617 = 1561666212 / (1 + 5 + 6 + 1 + 6 + 6 + 6 + 2 + 1 + 2).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 21689773 + ... + 21689844.

Almost surely, 2^1561666212 is an apocalyptic number.

1561666212 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

1561666212 is an abundant number, since it is smaller than the sum of its proper divisors (2385879026).

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

1561666212 is a wasteful number, since it uses less digits than its factorization.

1561666212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43379627 (or 43379622 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 1561666212 is about 39517.9226680756. The cubic root of 1561666212 is about 1160.1907662876.

The spelling of 1561666212 in words is "one billion, five hundred sixty-one million, six hundred sixty-six thousand, two hundred twelve".