1661667220 has 12 divisors (see below), whose sum is σ = 3489501204. Its totient is φ = 664666880.

The previous prime is 1661667191. The next prime is 1661667247. The reversal of 1661667220 is 227661661.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 182034064 + 1479633156 = 13492^2 + 38466^2 .

It is a super-2 number, since 2×1661667220² = 5522275900045056800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1661667220.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41541661 + ... + 41541700.

It is an arithmetic number, because the mean of its divisors is an integer number (290791767).

Almost surely, 2^1661667220 is an apocalyptic number.

1661667220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661667220 is an abundant number, since it is smaller than the sum of its proper divisors (1827833984).

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

1661667220 is a wasteful number, since it uses less digits than its factorization.

1661667220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83083370 (or 83083368 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 37.

The square root of 1661667220 is about 40763.5525929721. The cubic root of 1661667220 is about 1184.4444142570. Note that the first 4 decimals are identical.

The spelling of 1661667220 in words is "one billion, six hundred sixty-one million, six hundred sixty-seven thousand, two hundred twenty".