664961169421 has 2 divisors, whose sum is σ = 664961169422. Its totient is φ = 664961169420.

The previous prime is 664961169407. The next prime is 664961169479. The reversal of 664961169421 is 124961169466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 409617920196 + 255343249225 = 640014^2 + 505315^2 .

It is a cyclic number.

It is not a de Polignac number, because 664961169421 - 2⁷ = 664961169293 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664961169401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332480584710 + 332480584711.

It is an arithmetic number, because the mean of its divisors is an integer number (332480584711).

Almost surely, 2^664961169421 is an apocalyptic number.

It is an amenable number.

664961169421 is a deficient number, since it is larger than the sum of its proper divisors (1).

664961169421 is an equidigital number, since it uses as much as digits as its factorization.

664961169421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3359232, while the sum is 55.

The spelling of 664961169421 in words is "six hundred sixty-four billion, nine hundred sixty-one million, one hundred sixty-nine thousand, four hundred twenty-one".