1661265671 has 4 divisors (see below), whose sum is σ = 1789055352. Its totient is φ = 1533475992.

The previous prime is 1661265659. The next prime is 1661265691. The reversal of 1661265671 is 1765621661.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1661265671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661265611) 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, 63894821 + ... + 63894846.

It is an arithmetic number, because the mean of its divisors is an integer number (447263838).

Almost surely, 2^1661265671 is an apocalyptic number.

1661265671 is a deficient number, since it is larger than the sum of its proper divisors (127789681).

1661265671 is a wasteful number, since it uses less digits than its factorization.

1661265671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127789680.

The product of its digits is 90720, while the sum is 41.

The square root of 1661265671 is about 40758.6269518491. The cubic root of 1661265671 is about 1184.3489978822.

The spelling of 1661265671 in words is "one billion, six hundred sixty-one million, two hundred sixty-five thousand, six hundred seventy-one".