817637921 has 2 divisors, whose sum is σ = 817637922. Its totient is φ = 817637920.

The previous prime is 817637851. The next prime is 817637959. The reversal of 817637921 is 129736718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 537544225 + 280093696 = 23185^2 + 16736^2 .

It is a cyclic number.

It is not a de Polignac number, because 817637921 - 2²⁶ = 750529057 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (817636921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 408818960 + 408818961.

It is an arithmetic number, because the mean of its divisors is an integer number (408818961).

Almost surely, 2^817637921 is an apocalyptic number.

It is an amenable number.

817637921 is a deficient number, since it is larger than the sum of its proper divisors (1).

817637921 is an equidigital number, since it uses as much as digits as its factorization.

817637921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 127008, while the sum is 44.

The square root of 817637921 is about 28594.3686938530. The cubic root of 817637921 is about 935.0905651644.

The spelling of 817637921 in words is "eight hundred seventeen million, six hundred thirty-seven thousand, nine hundred twenty-one".