1661451563 has 4 divisors (see below), whose sum is σ = 1668707040. Its totient is φ = 1654196088.

The previous prime is 1661451553. The next prime is 1661451593. The reversal of 1661451563 is 3651541661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3651541661 = 48463 ⋅75347.

It is a cyclic number.

It is not a de Polignac number, because 1661451563 - 2¹⁸ = 1661189419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661451553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3627395 + ... + 3627852.

It is an arithmetic number, because the mean of its divisors is an integer number (417176760).

Almost surely, 2^1661451563 is an apocalyptic number.

1661451563 is a deficient number, since it is larger than the sum of its proper divisors (7255477).

1661451563 is an equidigital number, since it uses as much as digits as its factorization.

1661451563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7255476.

The product of its digits is 64800, while the sum is 38.

The square root of 1661451563 is about 40760.9072887246. The cubic root of 1661451563 is about 1184.3931715900.

The spelling of 1661451563 in words is "one billion, six hundred sixty-one million, four hundred fifty-one thousand, five hundred sixty-three".