1649867981 has 2 divisors, whose sum is σ = 1649867982. Its totient is φ = 1649867980.

The previous prime is 1649867959. The next prime is 1649868013. The reversal of 1649867981 is 1897689461.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1032593956 + 617274025 = 32134^2 + 24845^2 .

It is an emirp because it is prime and its reverse (1897689461) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1649867981 is a prime.

It is a super-2 number, since 2×1649867981² = 5444128709458032722, 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 1649867981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1649867381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 824933990 + 824933991.

It is an arithmetic number, because the mean of its divisors is an integer number (824933991).

Almost surely, 2^1649867981 is an apocalyptic number.

It is an amenable number.

1649867981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1649867981 is an equidigital number, since it uses as much as digits as its factorization.

1649867981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5225472, while the sum is 59.

The square root of 1649867981 is about 40618.5669491182. The cubic root of 1649867981 is about 1181.6342340046.

The spelling of 1649867981 in words is "one billion, six hundred forty-nine million, eight hundred sixty-seven thousand, nine hundred eighty-one".