1661688403 has 4 divisors (see below), whose sum is σ = 1661911288. Its totient is φ = 1661465520.

The previous prime is 1661688293. The next prime is 1661688551. The reversal of 1661688403 is 3048861661.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1661688403 - 2²¹ = 1659591251 is a prime.

It is a super-2 number, since 2×1661688403² = 5522416697329380818, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1661688403.

It is not an unprimeable number, because it can be changed into a prime (1665688403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99858 + ... + 115303.

It is an arithmetic number, because the mean of its divisors is an integer number (415477822).

Almost surely, 2^1661688403 is an apocalyptic number.

1661688403 is a deficient number, since it is larger than the sum of its proper divisors (222885).

1661688403 is an equidigital number, since it uses as much as digits as its factorization.

1661688403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222884.

The product of its (nonzero) digits is 165888, while the sum is 43.

The square root of 1661688403 is about 40763.8124198412. The cubic root of 1661688403 is about 1184.4494473505.

The spelling of 1661688403 in words is "one billion, six hundred sixty-one million, six hundred eighty-eight thousand, four hundred three".