321561640 has 32 divisors (see below), whose sum is σ = 726009480. Its totient is φ = 128180992.

The previous prime is 321561637. The next prime is 321561641. The reversal of 321561640 is 46165123.

It can be written as a sum of positive squares in 4 ways, for example, as 312087556 + 9474084 = 17666^2 + 3078^2 .

It is a junction number, because it is equal to n+sod(n) for n = 321561599 and 321561608.

It is not an unprimeable number, because it can be changed into a prime (321561641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1999 + ... + 25438.

Almost surely, 2^321561640 is an apocalyptic number.

It is an amenable number.

321561640 is an abundant number, since it is smaller than the sum of its proper divisors (404447840).

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

321561640 is a wasteful number, since it uses less digits than its factorization.

321561640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27741 (or 27737 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 321561640 is about 17932.1398611543. The cubic root of 321561640 is about 685.1012264491.

The spelling of 321561640 in words is "three hundred twenty-one million, five hundred sixty-one thousand, six hundred forty".