665025421 has 2 divisors, whose sum is σ = 665025422. Its totient is φ = 665025420.

The previous prime is 665025409. The next prime is 665025461. The reversal of 665025421 is 124520566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 504496521 + 160528900 = 22461^2 + 12670^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665025421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665025461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332512710 + 332512711.

It is an arithmetic number, because the mean of its divisors is an integer number (332512711).

Almost surely, 2^665025421 is an apocalyptic number.

It is an amenable number.

665025421 is a deficient number, since it is larger than the sum of its proper divisors (1).

665025421 is an equidigital number, since it uses as much as digits as its factorization.

665025421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14400, while the sum is 31.

The square root of 665025421 is about 25788.0868037937. The cubic root of 665025421 is about 872.8629955661.

Adding to 665025421 its reverse (124520566), we get a palindrome (789545987).

The spelling of 665025421 in words is "six hundred sixty-five million, twenty-five thousand, four hundred twenty-one".