648978721 has 2 divisors, whose sum is σ = 648978722. Its totient is φ = 648978720.

The previous prime is 648978719. The next prime is 648978751. The reversal of 648978721 is 127879846.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 637007121 + 11971600 = 25239^2 + 3460^2 .

It is a cyclic number.

It is not a de Polignac number, because 648978721 - 2¹ = 648978719 is a prime.

Together with 648978719, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (648978751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 324489360 + 324489361.

It is an arithmetic number, because the mean of its divisors is an integer number (324489361).

Almost surely, 2^648978721 is an apocalyptic number.

It is an amenable number.

648978721 is a deficient number, since it is larger than the sum of its proper divisors (1).

648978721 is an equidigital number, since it uses as much as digits as its factorization.

648978721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1354752, while the sum is 52.

The square root of 648978721 is about 25475.0607653839. The cubic root of 648978721 is about 865.7851896774.

The spelling of 648978721 in words is "six hundred forty-eight million, nine hundred seventy-eight thousand, seven hundred twenty-one".