1690020781 has 2 divisors, whose sum is σ = 1690020782. Its totient is φ = 1690020780.

The previous prime is 1690020767. The next prime is 1690020869. The reversal of 1690020781 is 1870200961.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 886014756 + 804006025 = 29766^2 + 28355^2 .

It is an emirp because it is prime and its reverse (1870200961) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1690020781 - 2⁷ = 1690020653 is a prime.

It is a super-2 number, since 2×1690020781² = 5712340480423699922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1690020181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 845010390 + 845010391.

It is an arithmetic number, because the mean of its divisors is an integer number (845010391).

Almost surely, 2^1690020781 is an apocalyptic number.

It is an amenable number.

1690020781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1690020781 is an equidigital number, since it uses as much as digits as its factorization.

1690020781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 1690020781 is about 41109.8623325352. The cubic root of 1690020781 is about 1191.1433074343.

The spelling of 1690020781 in words is "one billion, six hundred ninety million, twenty thousand, seven hundred eighty-one".