661284864 has 96 divisors (see below), whose sum is σ = 1959048000. Its totient is φ = 220409856.

The previous prime is 661284857. The next prime is 661284893. The reversal of 661284864 is 468482166.

It is a tau number, because it is divible by the number of its divisors (96).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

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, 49317 + ... + 61275.

It is an arithmetic number, because the mean of its divisors is an integer number (20406750).

Almost surely, 2^661284864 is an apocalyptic number.

661284864 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661284864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (979524000).

661284864 is an abundant number, since it is smaller than the sum of its proper divisors (1297763136).

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

661284864 is a wasteful number, since it uses less digits than its factorization.

661284864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11990 (or 11964 counting only the distinct ones).

The product of its digits is 442368, while the sum is 45.

The square root of 661284864 is about 25715.4596303469. The cubic root of 661284864 is about 871.2233918239.

The spelling of 661284864 in words is "six hundred sixty-one million, two hundred eighty-four thousand, eight hundred sixty-four".