1581364781 has 2 divisors, whose sum is σ = 1581364782. Its totient is φ = 1581364780.

The previous prime is 1581364691. The next prime is 1581364783. The reversal of 1581364781 is 1874631851.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1120575625 + 460789156 = 33475^2 + 21466^2 .

It is a cyclic number.

It is not a de Polignac number, because 1581364781 - 2¹⁸ = 1581102637 is a prime.

It is a super-2 number, since 2×1581364781² = 5001429141174355922, which contains 22 as substring.

Together with 1581364783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1581364783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 790682390 + 790682391.

It is an arithmetic number, because the mean of its divisors is an integer number (790682391).

Almost surely, 2^1581364781 is an apocalyptic number.

It is an amenable number.

1581364781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1581364781 is an equidigital number, since it uses as much as digits as its factorization.

1581364781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 161280, while the sum is 44.

The square root of 1581364781 is about 39766.3775192058. The cubic root of 1581364781 is about 1165.0485421269.

The spelling of 1581364781 in words is "one billion, five hundred eighty-one million, three hundred sixty-four thousand, seven hundred eighty-one".