648740821 has 2 divisors, whose sum is σ = 648740822. Its totient is φ = 648740820.

The previous prime is 648740819. The next prime is 648740863. The reversal of 648740821 is 128047846.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 542424100 + 106316721 = 23290^2 + 10311^2 .

It is a cyclic number.

It is not a de Polignac number, because 648740821 - 2¹ = 648740819 is a prime.

Together with 648740819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (648740801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 324370410 + 324370411.

It is an arithmetic number, because the mean of its divisors is an integer number (324370411).

Almost surely, 2^648740821 is an apocalyptic number.

It is an amenable number.

648740821 is a deficient number, since it is larger than the sum of its proper divisors (1).

648740821 is an equidigital number, since it uses as much as digits as its factorization.

648740821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 86016, while the sum is 40.

The square root of 648740821 is about 25470.3910649209. The cubic root of 648740821 is about 865.6793847345.

The spelling of 648740821 in words is "six hundred forty-eight million, seven hundred forty thousand, eight hundred twenty-one".