661321578 has 16 divisors (see below), whose sum is σ = 1324794240. Its totient is φ = 220082016.

The previous prime is 661321567. The next prime is 661321579. The reversal of 661321578 is 875123166.

It is not an unprimeable number, because it can be changed into a prime (661321579) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 85618 + ... + 93021.

It is an arithmetic number, because the mean of its divisors is an integer number (82799640).

Almost surely, 2^661321578 is an apocalyptic number.

661321578 is an abundant number, since it is smaller than the sum of its proper divisors (663472662).

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

661321578 is a wasteful number, since it uses less digits than its factorization.

661321578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 179261.

The product of its digits is 60480, while the sum is 39.

The square root of 661321578 is about 25716.1734711835. The cubic root of 661321578 is about 871.2395147312.

The spelling of 661321578 in words is "six hundred sixty-one million, three hundred twenty-one thousand, five hundred seventy-eight".