1661433637 has 4 divisors (see below), whose sum is σ = 1688670316. Its totient is φ = 1634196960.

The previous prime is 1661433629. The next prime is 1661433643. The reversal of 1661433637 is 7363341661.

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

It can be written as a sum of positive squares in 2 ways, for example, as 472149441 + 1189284196 = 21729^2 + 34486^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661433637 - 2³ = 1661433629 is a prime.

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 1661433637.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661433617) 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, 13618248 + ... + 13618369.

It is an arithmetic number, because the mean of its divisors is an integer number (422167579).

Almost surely, 2^1661433637 is an apocalyptic number.

It is an amenable number.

1661433637 is a deficient number, since it is larger than the sum of its proper divisors (27236679).

1661433637 is an equidigital number, since it uses as much as digits as its factorization.

1661433637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27236678.

The product of its digits is 163296, while the sum is 40.

The square root of 1661433637 is about 40760.6873960683. The cubic root of 1661433637 is about 1184.3889119596.

The spelling of 1661433637 in words is "one billion, six hundred sixty-one million, four hundred thirty-three thousand, six hundred thirty-seven".