661563 has 12 divisors (see below), whose sum is σ = 1092208. Its totient is φ = 378000.

The previous prime is 661553. The next prime is 661603. The reversal of 661563 is 365166.

It is not a de Polignac number, because 661563 - 2⁴ = 661547 is a prime.

It is a Duffinian number.

661563 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (661513) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5188 + ... + 5313.

2⁶⁶¹⁵⁶³ is an apocalyptic number.

661563 is a gapful number since it is divisible by the number (63) formed by its first and last digit.

661563 is a deficient number, since it is larger than the sum of its proper divisors (430645).

661563 is a wasteful number, since it uses less digits than its factorization.

661563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10514 (or 10511 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 661563 is about 813.3652316149. The cubic root of 661563 is about 87.1345520041.

The spelling of 661563 in words is "six hundred sixty-one thousand, five hundred sixty-three".