1661783215 has 4 divisors (see below), whose sum is σ = 1994139864. Its totient is φ = 1329426568.

The previous prime is 1661783213. The next prime is 1661783231. The reversal of 1661783215 is 5123871661.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1661783215 - 2¹ = 1661783213 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661783213) 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, 166178317 + ... + 166178326.

It is an arithmetic number, because the mean of its divisors is an integer number (498534966).

Almost surely, 2^1661783215 is an apocalyptic number.

1661783215 is a deficient number, since it is larger than the sum of its proper divisors (332356649).

1661783215 is an equidigital number, since it uses as much as digits as its factorization.

1661783215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332356648.

The product of its digits is 60480, while the sum is 40.

The square root of 1661783215 is about 40764.9753464908. The cubic root of 1661783215 is about 1184.4719742143.

The spelling of 1661783215 in words is "one billion, six hundred sixty-one million, seven hundred eighty-three thousand, two hundred fifteen".