661616216 has 8 divisors (see below), whose sum is σ = 1240530420. Its totient is φ = 330808104.

The previous prime is 661616209. The next prime is 661616239. The reversal of 661616216 is 612616166.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41351006 + ... + 41351021.

Almost surely, 2^661616216 is an apocalyptic number.

It is an amenable number.

661616216 is a deficient number, since it is larger than the sum of its proper divisors (578914204).

661616216 is a wasteful number, since it uses less digits than its factorization.

661616216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82702033 (or 82702029 counting only the distinct ones).

The product of its digits is 15552, while the sum is 35.

The square root of 661616216 is about 25721.9014849214. The cubic root of 661616216 is about 871.3688830363.

Subtracting from 661616216 its reverse (612616166), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 661616216 in words is "six hundred sixty-one million, six hundred sixteen thousand, two hundred sixteen".