1661002020 has 72 divisors (see below), whose sum is σ = 5043814776. Its totient is φ = 442455552.

The previous prime is 1661002009. The next prime is 1661002027. The reversal of 1661002020 is 202001661.

It is a happy number.

1661002020 is a `hidden beast` number, since 1 + 661 + 0 + 0 + 2 + 0 + 2 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 372335616 + 1288666404 = 19296^2 + 35898^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 1661001984 and 1661002002.

It is not an unprimeable number, because it can be changed into a prime (1661002027) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 181474 + ... + 190406.

It is an arithmetic number, because the mean of its divisors is an integer number (70052983).

Almost surely, 2^1661002020 is an apocalyptic number.

1661002020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661002020 is an abundant number, since it is smaller than the sum of its proper divisors (3382812756).

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

1661002020 is a wasteful number, since it uses less digits than its factorization.

1661002020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9981 (or 9976 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 1661002020 is about 40755.3925266338. The cubic root of 1661002020 is about 1184.2863405715.

Adding to 1661002020 its reverse (202001661), we get a palindrome (1863003681).

The spelling of 1661002020 in words is "one billion, six hundred sixty-one million, two thousand, twenty".