1661979816 has 128 divisors (see below), whose sum is σ = 5505638400. Its totient is φ = 454196160.

The previous prime is 1661979773. The next prime is 1661979817. The reversal of 1661979816 is 6189791661.

It is a happy number.

1661979816 is a `hidden beast` number, since 1 + 6 + 619 + 7 + 9 + 8 + 16 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (1661979817) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10881 + ... + 58671.

It is an arithmetic number, because the mean of its divisors is an integer number (43012800).

Almost surely, 2^1661979816 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661979816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2752819200).

1661979816 is an abundant number, since it is smaller than the sum of its proper divisors (3843658584).

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

1661979816 is a wasteful number, since it uses less digits than its factorization.

1661979816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47836 (or 47826 counting only the distinct ones).

The product of its digits is 979776, while the sum is 54.

The square root of 1661979816 is about 40767.3866712106. The cubic root of 1661979816 is about 1184.5186829125.

The spelling of 1661979816 in words is "one billion, six hundred sixty-one million, nine hundred seventy-nine thousand, eight hundred sixteen".