1661553 has 20 divisors (see below), whose sum is σ = 2525028. Its totient is φ = 1088640.

The previous prime is 1661549. The next prime is 1661557. The reversal of 1661553 is 3551661.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1661549) and next prime (1661557).

It can be written as a sum of positive squares in 2 ways, for example, as 1034289 + 627264 = 1017^2 + 792^2 .

It is not a de Polignac number, because 1661553 - 2² = 1661549 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1661557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 5773 + ... + 6053.

2^1661553 is an apocalyptic number.

It is an amenable number.

1661553 is a deficient number, since it is larger than the sum of its proper divisors (863475).

1661553 is an equidigital number, since it uses as much as digits as its factorization.

1661553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 366 (or 357 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The square root of 1661553 is about 1289.0124126633. The cubic root of 1661553 is about 118.4417274779.

The spelling of 1661553 in words is "one million, six hundred sixty-one thousand, five hundred fifty-three".