1661720 has 16 divisors (see below), whose sum is σ = 3738960. Its totient is φ = 664672.

The previous prime is 1661713. The next prime is 1661731. The reversal of 1661720 is 271661.

It is a super-2 number, since 2×1661720² = 5522626716800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20732 + ... + 20811.

It is an arithmetic number, because the mean of its divisors is an integer number (233685).

2^1661720 is an apocalyptic number.

1661720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1661720 is an abundant number, since it is smaller than the sum of its proper divisors (2077240).

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

1661720 is a wasteful number, since it uses less digits than its factorization.

1661720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41554 (or 41550 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 1661720 is about 1289.0771893102. The cubic root of 1661720 is about 118.4456954737.

The spelling of 1661720 in words is "one million, six hundred sixty-one thousand, seven hundred twenty".