999989681 has 2 divisors, whose sum is σ = 999989682. Its totient is φ = 999989680.

The previous prime is 999989647. The next prime is 999989689. The reversal of 999989681 is 186989999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624250225 + 375739456 = 24985^2 + 19384^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999989681 is a prime.

It is a super-2 number, since 2×999989681² = 1999958724212963522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (999989689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499994840 + 499994841.

It is an arithmetic number, because the mean of its divisors is an integer number (499994841).

Almost surely, 2^999989681 is an apocalyptic number.

It is an amenable number.

999989681 is a deficient number, since it is larger than the sum of its proper divisors (1).

999989681 is an equidigital number, since it uses as much as digits as its factorization.

999989681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22674816, while the sum is 68.

The square root of 999989681 is about 31622.6134435470. The cubic root of 999989681 is about 999.9965603215.

The spelling of 999989681 in words is "nine hundred ninety-nine million, nine hundred eighty-nine thousand, six hundred eighty-one".