1634611661 has 4 divisors (see below), whose sum is σ = 1641394524. Its totient is φ = 1627828800.

The previous prime is 1634611621. The next prime is 1634611691. The reversal of 1634611661 is 1661164361.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1661164361 = 5879 ⋅282559.

It can be written as a sum of positive squares in 2 ways, for example, as 895804900 + 738806761 = 29930^2 + 27181^2 .

It is a cyclic number.

It is not a de Polignac number, because 1634611661 - 2¹⁸ = 1634349517 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 (1634611621) 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, 3391070 + ... + 3391551.

It is an arithmetic number, because the mean of its divisors is an integer number (410348631).

Almost surely, 2^1634611661 is an apocalyptic number.

It is an amenable number.

1634611661 is a deficient number, since it is larger than the sum of its proper divisors (6782863).

1634611661 is an equidigital number, since it uses as much as digits as its factorization.

1634611661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6782862.

The product of its digits is 15552, while the sum is 35.

The square root of 1634611661 is about 40430.3309533820. The cubic root of 1634611661 is about 1177.9807611560.

The spelling of 1634611661 in words is "one billion, six hundred thirty-four million, six hundred eleven thousand, six hundred sixty-one".