661658 has 8 divisors (see below), whose sum is σ = 1016820. Its totient is φ = 322720.

The previous prime is 661621. The next prime is 661663. The reversal of 661658 is 856166.

Added to its reverse (856166) it gives a square (1517824 = 1232²).

It can be written as a sum of positive squares in 2 ways, for example, as 418609 + 243049 = 647^2 + 493^2 .

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

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661658.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3953 + ... + 4116.

2⁶⁶¹⁶⁵⁸ is an apocalyptic number.

661658 is a deficient number, since it is larger than the sum of its proper divisors (355162).

661658 is a wasteful number, since it uses less digits than its factorization.

661658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8112.

The product of its digits is 8640, while the sum is 32.

The square root of 661658 is about 813.4236288675. The cubic root of 661658 is about 87.1387226254.

Adding to 661658 its reverse (856166), we get a square (1517824 = 1232²).

The spelling of 661658 in words is "six hundred sixty-one thousand, six hundred fifty-eight".