661642216 has 16 divisors (see below), whose sum is σ = 1257574500. Its totient is φ = 326289024.

The previous prime is 661642211. The next prime is 661642229. The reversal of 661642216 is 612246166.

It can be written as a sum of positive squares in 2 ways, for example, as 602506116 + 59136100 = 24546^2 + 7690^2 .

It is not an unprimeable number, because it can be changed into a prime (661642211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 565891 + ... + 567058.

Almost surely, 2^661642216 is an apocalyptic number.

It is an amenable number.

661642216 is a deficient number, since it is larger than the sum of its proper divisors (595932284).

661642216 is a wasteful number, since it uses less digits than its factorization.

661642216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1133028 (or 1133024 counting only the distinct ones).

The product of its digits is 20736, while the sum is 34.

The square root of 661642216 is about 25722.4068858262. The cubic root of 661642216 is about 871.3802971530.

The spelling of 661642216 in words is "six hundred sixty-one million, six hundred forty-two thousand, two hundred sixteen".