1531711981 has 2 divisors, whose sum is σ = 1531711982. Its totient is φ = 1531711980.

The previous prime is 1531711967. The next prime is 1531712003. The reversal of 1531711981 is 1891171351.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1206450756 + 325261225 = 34734^2 + 18035^2 .

It is a cyclic number.

It is not a de Polignac number, because 1531711981 - 2⁹ = 1531711469 is a prime.

It is a super-2 number, since 2×1531711981² = 4692283185477888722, 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 1531711981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1531751981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 765855990 + 765855991.

It is an arithmetic number, because the mean of its divisors is an integer number (765855991).

Almost surely, 2^1531711981 is an apocalyptic number.

It is an amenable number.

1531711981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1531711981 is an equidigital number, since it uses as much as digits as its factorization.

1531711981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7560, while the sum is 37.

The square root of 1531711981 is about 39137.0921377662. The cubic root of 1531711981 is about 1152.7249761331.

The spelling of 1531711981 in words is "one billion, five hundred thirty-one million, seven hundred eleven thousand, nine hundred eighty-one".