667521389 has 2 divisors, whose sum is σ = 667521390. Its totient is φ = 667521388.

The previous prime is 667521383. The next prime is 667521427. The reversal of 667521389 is 983125766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 547794025 + 119727364 = 23405^2 + 10942^2 .

It is a cyclic number.

It is not a de Polignac number, because 667521389 - 2²⁸ = 399085933 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (667521383) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333760694 + 333760695.

It is an arithmetic number, because the mean of its divisors is an integer number (333760695).

Almost surely, 2^667521389 is an apocalyptic number.

It is an amenable number.

667521389 is a deficient number, since it is larger than the sum of its proper divisors (1).

667521389 is an equidigital number, since it uses as much as digits as its factorization.

667521389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 544320, while the sum is 47.

The square root of 667521389 is about 25836.4352997855. The cubic root of 667521389 is about 873.9536396678.

The spelling of 667521389 in words is "six hundred sixty-seven million, five hundred twenty-one thousand, three hundred eighty-nine".