661215663 has 16 divisors (see below), whose sum is σ = 1037201760. Its totient is φ = 414880128.

The previous prime is 661215649. The next prime is 661215671. The reversal of 661215663 is 366512166.

It is not a de Polignac number, because 661215663 - 2⁸ = 661215407 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661215613) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 719820 + ... + 720737.

It is an arithmetic number, because the mean of its divisors is an integer number (64825110).

Almost surely, 2^661215663 is an apocalyptic number.

661215663 is a deficient number, since it is larger than the sum of its proper divisors (375986097).

661215663 is a wasteful number, since it uses less digits than its factorization.

661215663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1440583 (or 1440577 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 661215663 is about 25714.1140815701. The cubic root of 661215663 is about 871.1930006685.

The spelling of 661215663 in words is "six hundred sixty-one million, two hundred fifteen thousand, six hundred sixty-three".