781721851 has 2 divisors, whose sum is σ = 781721852. Its totient is φ = 781721850.

The previous prime is 781721789. The next prime is 781721869. The reversal of 781721851 is 158127187.

781721851 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 781721851 - 2¹¹ = 781719803 is a prime.

It is a super-2 number, since 2×781721851² = 1222178104661732402, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (781721881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 390860925 + 390860926.

It is an arithmetic number, because the mean of its divisors is an integer number (390860926).

Almost surely, 2^781721851 is an apocalyptic number.

781721851 is a deficient number, since it is larger than the sum of its proper divisors (1).

781721851 is an equidigital number, since it uses as much as digits as its factorization.

781721851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31360, while the sum is 40.

The square root of 781721851 is about 27959.2891719371. The cubic root of 781721851 is about 921.1932574976.

The spelling of 781721851 in words is "seven hundred eighty-one million, seven hundred twenty-one thousand, eight hundred fifty-one".