664478512421 has 2 divisors, whose sum is σ = 664478512422. Its totient is φ = 664478512420.

The previous prime is 664478512393. The next prime is 664478512427. The reversal of 664478512421 is 124215874466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 560942579521 + 103535932900 = 748961^2 + 321770^2 .

It is a cyclic number.

It is not a de Polignac number, because 664478512421 - 2¹⁰ = 664478511397 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 664478512421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664478512427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332239256210 + 332239256211.

It is an arithmetic number, because the mean of its divisors is an integer number (332239256211).

Almost surely, 2^664478512421 is an apocalyptic number.

It is an amenable number.

664478512421 is a deficient number, since it is larger than the sum of its proper divisors (1).

664478512421 is an equidigital number, since it uses as much as digits as its factorization.

664478512421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2580480, while the sum is 50.

The spelling of 664478512421 in words is "six hundred sixty-four billion, four hundred seventy-eight million, five hundred twelve thousand, four hundred twenty-one".