1659994781 has 2 divisors, whose sum is σ = 1659994782. Its totient is φ = 1659994780.

The previous prime is 1659994729. The next prime is 1659994783. The reversal of 1659994781 is 1874999561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 835788100 + 824206681 = 28910^2 + 28709^2 .

It is an emirp because it is prime and its reverse (1874999561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1659994781 - 2²² = 1655800477 is a prime.

It is a super-2 number, since 2×1659994781² = 5511165345894475922, which contains 22 as substring.

Together with 1659994783, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1659994781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1659994783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 829997390 + 829997391.

It is an arithmetic number, because the mean of its divisors is an integer number (829997391).

Almost surely, 2^1659994781 is an apocalyptic number.

It is an amenable number.

1659994781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1659994781 is an equidigital number, since it uses as much as digits as its factorization.

1659994781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4898880, while the sum is 59.

The square root of 1659994781 is about 40743.0335272179. The cubic root of 1659994781 is about 1184.0469066686.

The spelling of 1659994781 in words is "one billion, six hundred fifty-nine million, nine hundred ninety-four thousand, seven hundred eighty-one".