661797216 has 240 divisors, whose sum is σ = 2153710944. Its totient is φ = 198291456.

The previous prime is 661797211. The next prime is 661797221. The reversal of 661797216 is 612797166.

It is a happy number.

661797216 is a `hidden beast` number, since 6 + 617 + 9 + 7 + 21 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (661797211) and next prime (661797221).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661797211) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1013146 + ... + 1013798.

Almost surely, 2^661797216 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 661797216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1076855472).

661797216 is an abundant number, since it is smaller than the sum of its proper divisors (1491913728).

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

661797216 is a wasteful number, since it uses less digits than its factorization.

661797216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 715 (or 698 counting only the distinct ones).

The product of its digits is 190512, while the sum is 45.

The square root of 661797216 is about 25725.4196467230. The cubic root of 661797216 is about 871.4483366449.

Subtracting from 661797216 its reverse (612797166), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 661797216 in words is "six hundred sixty-one million, seven hundred ninety-seven thousand, two hundred sixteen".