1566216217 has 4 divisors (see below), whose sum is σ = 1568822836. Its totient is φ = 1563609600.

The previous prime is 1566216209. The next prime is 1566216221. The reversal of 1566216217 is 7126126651.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 844541721 + 721674496 = 29061^2 + 26864^2 .

It is a cyclic number.

It is not a de Polignac number, because 1566216217 - 2³ = 1566216209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1566216287) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1302408 + ... + 1303609.

It is an arithmetic number, because the mean of its divisors is an integer number (392205709).

Almost surely, 2^1566216217 is an apocalyptic number.

It is an amenable number.

1566216217 is a deficient number, since it is larger than the sum of its proper divisors (2606619).

1566216217 is an equidigital number, since it uses as much as digits as its factorization.

1566216217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2606618.

The product of its digits is 30240, while the sum is 37.

The square root of 1566216217 is about 39575.4496752722. The cubic root of 1566216217 is about 1161.3164347693.

The spelling of 1566216217 in words is "one billion, five hundred sixty-six million, two hundred sixteen thousand, two hundred seventeen".