1571981981 has 2 divisors, whose sum is σ = 1571981982. Its totient is φ = 1571981980.

The previous prime is 1571981951. The next prime is 1571981987. The reversal of 1571981981 is 1891891751.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1215149881 + 356832100 = 34859^2 + 18890^2 .

It is an emirp because it is prime and its reverse (1891891751) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1571981981 - 2¹⁴ = 1571965597 is a prime.

It is a super-2 number, since 2×1571981981² = 4942254697177368722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1571981987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 785990990 + 785990991.

It is an arithmetic number, because the mean of its divisors is an integer number (785990991).

Almost surely, 2^1571981981 is an apocalyptic number.

It is an amenable number.

1571981981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1571981981 is an equidigital number, since it uses as much as digits as its factorization.

1571981981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 181440, while the sum is 50.

The square root of 1571981981 is about 39648.2279679685. The cubic root of 1571981981 is about 1162.7397539336.

The spelling of 1571981981 in words is "one billion, five hundred seventy-one million, nine hundred eighty-one thousand, nine hundred eighty-one".