661578 has 16 divisors (see below), whose sum is σ = 1342656. Its totient is φ = 217280.

The previous prime is 661553. The next prime is 661603. The reversal of 661578 is 875166.

It is an interprime number because it is at equal distance from previous prime (661553) and next prime (661603).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 351 + ... + 1202.

It is an arithmetic number, because the mean of its divisors is an integer number (83916).

2⁶⁶¹⁵⁷⁸ is an apocalyptic number.

661578 is an abundant number, since it is smaller than the sum of its proper divisors (681078).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661578 is a wasteful number, since it uses less digits than its factorization.

661578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1629.

The product of its digits is 10080, while the sum is 33.

The square root of 661578 is about 813.3744525125. The cubic root of 661578 is about 87.1352105498.

The spelling of 661578 in words is "six hundred sixty-one thousand, five hundred seventy-eight".