661747216 has 120 divisors (see below), whose sum is σ = 1463906304. Its totient is φ = 289336320.

The previous prime is 661747211. The next prime is 661747217. The reversal of 661747216 is 612747166.

It is not an unprimeable number, because it can be changed into a prime (661747211) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5210545 + ... + 5210671.

Almost surely, 2^661747216 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 661747216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (731953152).

661747216 is an abundant number, since it is smaller than the sum of its proper divisors (802159088).

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

661747216 is a wasteful number, since it uses less digits than its factorization.

661747216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249 (or 230 counting only the distinct ones).

The product of its digits is 84672, while the sum is 40.

The square root of 661747216 is about 25724.4478269214. The cubic root of 661747216 is about 871.4263895826.

Subtracting from 661747216 its reverse (612747166), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 661747216 in words is "six hundred sixty-one million, seven hundred forty-seven thousand, two hundred sixteen".