661634543 has 4 divisors (see below), whose sum is σ = 700554240. Its totient is φ = 622714848.

The previous prime is 661634539. The next prime is 661634569. The reversal of 661634543 is 345436166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 345436166 = 2 ⋅172718083.

It is a cyclic number.

It is not a de Polignac number, because 661634543 - 2² = 661634539 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661634497 and 661634506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661634143) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19459823 + ... + 19459856.

It is an arithmetic number, because the mean of its divisors is an integer number (175138560).

Almost surely, 2^661634543 is an apocalyptic number.

661634543 is a deficient number, since it is larger than the sum of its proper divisors (38919697).

661634543 is a wasteful number, since it uses less digits than its factorization.

661634543 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38919696.

The product of its digits is 155520, while the sum is 38.

The square root of 661634543 is about 25722.2577352767. The cubic root of 661634543 is about 871.3769287027.

The spelling of 661634543 in words is "six hundred sixty-one million, six hundred thirty-four thousand, five hundred forty-three".