1661980 has 24 divisors (see below), whose sum is σ = 3642912. Its totient is φ = 635712.

The previous prime is 1661977. The next prime is 1661983. The reversal of 1661980 is 891661.

1661980 = T₈₁ + T₈₂ + ... + T₂₁₈.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1661977) and next prime (1661983).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661983) 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, 1347 + ... + 2266.

It is an arithmetic number, because the mean of its divisors is an integer number (151788).

2^1661980 is an apocalyptic number.

1661980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661980 is an abundant number, since it is smaller than the sum of its proper divisors (1980932).

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

1661980 is a wasteful number, since it uses less digits than its factorization.

1661980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3645 (or 3643 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 1661980 is about 1289.1780327015. The cubic root of 1661980 is about 118.4518726626.

The spelling of 1661980 in words is "one million, six hundred sixty-one thousand, nine hundred eighty".