1899509981 has 2 divisors, whose sum is σ = 1899509982. Its totient is φ = 1899509980.

The previous prime is 1899509957. The next prime is 1899510013. The reversal of 1899509981 is 1899059981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1692005956 + 207504025 = 41134^2 + 14405^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1899509981 is a prime.

It is a super-2 number, since 2×1899509981² = 7216276335837240722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1899509981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1899509681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 949754990 + 949754991.

It is an arithmetic number, because the mean of its divisors is an integer number (949754991).

Almost surely, 2^1899509981 is an apocalyptic number.

It is an amenable number.

1899509981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1899509981 is an equidigital number, since it uses as much as digits as its factorization.

1899509981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2099520, while the sum is 59.

The square root of 1899509981 is about 43583.3681695208. The cubic root of 1899509981 is about 1238.4558434447.

The spelling of 1899509981 in words is "one billion, eight hundred ninety-nine million, five hundred nine thousand, nine hundred eighty-one".