1665642547 has 4 divisors (see below), whose sum is σ = 1666785640. Its totient is φ = 1664499456.

The previous prime is 1665642523. The next prime is 1665642577. The reversal of 1665642547 is 7452465661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7452465661 = 17 ⋅438380333.

It is a cyclic number.

It is not a de Polignac number, because 1665642547 - 2¹¹ = 1665640499 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1665642497 and 1665642506.

It is not an unprimeable number, because it can be changed into a prime (1665642577) 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, 569358 + ... + 572275.

It is an arithmetic number, because the mean of its divisors is an integer number (416696410).

Almost surely, 2^1665642547 is an apocalyptic number.

1665642547 is a deficient number, since it is larger than the sum of its proper divisors (1143093).

1665642547 is a wasteful number, since it uses less digits than its factorization.

1665642547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1143092.

The product of its digits is 1209600, while the sum is 46.

The square root of 1665642547 is about 40812.2842658923. The cubic root of 1665642547 is about 1185.3882061134.

The spelling of 1665642547 in words is "one billion, six hundred sixty-five million, six hundred forty-two thousand, five hundred forty-seven".