661646 has 4 divisors (see below), whose sum is σ = 992472. Its totient is φ = 330822.

The previous prime is 661621. The next prime is 661663. The reversal of 661646 is 646166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 646166 = 2 ⋅323083.

It is a congruent number.

It is an unprimeable number.

661646 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 as a sum of consecutive naturals, namely, 165410 + ... + 165413.

It is an arithmetic number, because the mean of its divisors is an integer number (248118).

2⁶⁶¹⁶⁴⁶ is an apocalyptic number.

661646 is a deficient number, since it is larger than the sum of its proper divisors (330826).

661646 is a wasteful number, since it uses less digits than its factorization.

661646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 330825.

The product of its digits is 5184, while the sum is 29.

The square root of 661646 is about 813.4162526038. The cubic root of 661646 is about 87.1381958321.

The spelling of 661646 in words is "six hundred sixty-one thousand, six hundred forty-six".