661276656 has 80 divisors (see below), whose sum is σ = 1909957120. Its totient is φ = 219049920.

The previous prime is 661276639. The next prime is 661276673. The reversal of 661276656 is 656672166.

It is an interprime number because it is at equal distance from previous prime (661276639) and next prime (661276673).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 65721 + ... + 75111.

It is an arithmetic number, because the mean of its divisors is an integer number (23874464).

Almost surely, 2^661276656 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 661276656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (954978560).

661276656 is an abundant number, since it is smaller than the sum of its proper divisors (1248680464).

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

661276656 is a wasteful number, since it uses less digits than its factorization.

661276656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9571 (or 9559 counting only the distinct ones).

The product of its digits is 544320, while the sum is 45.

The square root of 661276656 is about 25715.3000371374. The cubic root of 661276656 is about 871.2197872093.

The spelling of 661276656 in words is "six hundred sixty-one million, two hundred seventy-six thousand, six hundred fifty-six".