661897216 has 60 divisors (see below), whose sum is σ = 1344757680. Its totient is φ = 325713920.

The previous prime is 661897207. The next prime is 661897217. The reversal of 661897216 is 612798166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661897217) 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 3 ways as a sum of consecutive naturals, for example, 1162980 + ... + 1163548.

It is an arithmetic number, because the mean of its divisors is an integer number (22412628).

Almost surely, 2^661897216 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661897216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (672378840).

661897216 is an abundant number, since it is smaller than the sum of its proper divisors (682860464).

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

661897216 is an frugal number, since it uses more digits than its factorization.

661897216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668 (or 642 counting only the distinct ones).

The product of its digits is 217728, while the sum is 46.

The square root of 661897216 is about 25727.3631761982. The cubic root of 661897216 is about 871.4922274535.

The spelling of 661897216 in words is "six hundred sixty-one million, eight hundred ninety-seven thousand, two hundred sixteen".