661538 has 8 divisors (see below), whose sum is σ = 1050732. Its totient is φ = 311296.

The previous prime is 661517. The next prime is 661541. The reversal of 661538 is 835166.

It can be written as a sum of positive squares in 2 ways, for example, as 597529 + 64009 = 773^2 + 253^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 661538.

It is an unprimeable number.

661538 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9695 + ... + 9762.

2⁶⁶¹⁵³⁸ is an apocalyptic number.

661538 is a deficient number, since it is larger than the sum of its proper divisors (389194).

661538 is a wasteful number, since it uses less digits than its factorization.

661538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19476.

The product of its digits is 4320, while the sum is 29.

The square root of 661538 is about 813.3498632200. The cubic root of 661538 is about 87.1334544058.

The spelling of 661538 in words is "six hundred sixty-one thousand, five hundred thirty-eight".