1663561565 has 8 divisors (see below), whose sum is σ = 1998374328. Its totient is φ = 1329448960.

The previous prime is 1663561553. The next prime is 1663561573. The reversal of 1663561565 is 5651653661.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 302099161 + 1361462404 = 17381^2 + 36898^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1663561565 - 2¹⁰ = 1663560541 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 169796 + ... + 179325.

It is an arithmetic number, because the mean of its divisors is an integer number (249796791).

Almost surely, 2^1663561565 is an apocalyptic number.

It is an amenable number.

1663561565 is a deficient number, since it is larger than the sum of its proper divisors (334812763).

1663561565 is an equidigital number, since it uses as much as digits as its factorization.

1663561565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 350079.

The product of its digits is 486000, while the sum is 44.

The square root of 1663561565 is about 40786.7817435992. The cubic root of 1663561565 is about 1184.8943427431.

The spelling of 1663561565 in words is "one billion, six hundred sixty-three million, five hundred sixty-one thousand, five hundred sixty-five".