1661323216 has 40 divisors (see below), whose sum is σ = 3872262080. Its totient is φ = 674521344.

The previous prime is 1661323207. The next prime is 1661323219. The reversal of 1661323216 is 6123231661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661323219) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 388221 + ... + 392476.

It is an arithmetic number, because the mean of its divisors is an integer number (96806552).

Almost surely, 2^1661323216 is an apocalyptic number.

1661323216 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1661323216 is an abundant number, since it is smaller than the sum of its proper divisors (2210938864).

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

1661323216 is a wasteful number, since it uses less digits than its factorization.

1661323216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780731 (or 780725 counting only the distinct ones).

The product of its digits is 7776, while the sum is 31.

The square root of 1661323216 is about 40759.3328699085. The cubic root of 1661323216 is about 1184.3626727121.

Adding to 1661323216 its reverse (6123231661), we get a palindrome (7784554877).

The spelling of 1661323216 in words is "one billion, six hundred sixty-one million, three hundred twenty-three thousand, two hundred sixteen".