781661493 has 6 divisors (see below), whose sum is σ = 1129066614. Its totient is φ = 521107656.

The previous prime is 781661477. The next prime is 781661557. The reversal of 781661493 is 394166187.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 753337809 + 28323684 = 27447^2 + 5322^2 .

It is not a de Polignac number, because 781661493 - 2⁴ = 781661477 is a prime.

It is a super-2 number, since 2×781661493² = 1221989379277978098, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781661093) 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 in 5 ways as a sum of consecutive naturals, for example, 43425630 + ... + 43425647.

It is an arithmetic number, because the mean of its divisors is an integer number (188177769).

Almost surely, 2^781661493 is an apocalyptic number.

It is an amenable number.

781661493 is a deficient number, since it is larger than the sum of its proper divisors (347405121).

781661493 is a wasteful number, since it uses less digits than its factorization.

781661493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86851283 (or 86851280 counting only the distinct ones).

The product of its digits is 217728, while the sum is 45.

The square root of 781661493 is about 27958.2097602833. The cubic root of 781661493 is about 921.1695479502.

The spelling of 781661493 in words is "seven hundred eighty-one million, six hundred sixty-one thousand, four hundred ninety-three".