648815991 has 4 divisors (see below), whose sum is σ = 865087992. Its totient is φ = 432543992.

The previous prime is 648815953. The next prime is 648816017. The reversal of 648815991 is 199518846.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 648815991 - 2¹¹ = 648813943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (648810991) 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, 108135996 + ... + 108136001.

It is an arithmetic number, because the mean of its divisors is an integer number (216271998).

Almost surely, 2^648815991 is an apocalyptic number.

648815991 is a deficient number, since it is larger than the sum of its proper divisors (216272001).

648815991 is a wasteful number, since it uses less digits than its factorization.

648815991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216272000.

The product of its digits is 622080, while the sum is 51.

The square root of 648815991 is about 25471.8666571573. The cubic root of 648815991 is about 865.7128190450.

The spelling of 648815991 in words is "six hundred forty-eight million, eight hundred fifteen thousand, nine hundred ninety-one".