999780433921 has 2 divisors, whose sum is σ = 999780433922. Its totient is φ = 999780433920.

The previous prime is 999780433901. The next prime is 999780433957. The reversal of 999780433921 is 129334087999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 606118303296 + 393662130625 = 778536^2 + 627425^2 .

It is an emirp because it is prime and its reverse (129334087999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999780433921 - 2⁷ = 999780433793 is a prime.

It is not a weakly prime, because it can be changed into another prime (999780433901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499890216960 + 499890216961.

It is an arithmetic number, because the mean of its divisors is an integer number (499890216961).

Almost surely, 2^999780433921 is an apocalyptic number.

It is an amenable number.

999780433921 is a deficient number, since it is larger than the sum of its proper divisors (1).

999780433921 is an equidigital number, since it uses as much as digits as its factorization.

999780433921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 26453952, while the sum is 64.

The spelling of 999780433921 in words is "nine hundred ninety-nine billion, seven hundred eighty million, four hundred thirty-three thousand, nine hundred twenty-one".