1661728 has 12 divisors (see below), whose sum is σ = 3271590. Its totient is φ = 830848.

The previous prime is 1661713. The next prime is 1661731. The reversal of 1661728 is 8271661.

It can be written as a sum of positive squares in only one way, i.e., 976144 + 685584 = 988^2 + 828^2 .

It is a super-2 number, since 2×1661728² = 5522679891968, which contains 22 as substring.

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661728.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25933 + ... + 25996.

2^1661728 is an apocalyptic number.

It is an amenable number.

1661728 is a deficient number, since it is larger than the sum of its proper divisors (1609862).

1661728 is an equidigital number, since it uses as much as digits as its factorization.

1661728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51939 (or 51931 counting only the distinct ones).

The product of its digits is 4032, while the sum is 31.

The square root of 1661728 is about 1289.0802923015. The cubic root of 1661728 is about 118.4458855507.

The spelling of 1661728 in words is "one million, six hundred sixty-one thousand, seven hundred twenty-eight".