781021681 has 8 divisors (see below), whose sum is σ = 853723584. Its totient is φ = 708603120.

The previous prime is 781021663. The next prime is 781021687. The reversal of 781021681 is 186120187.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-781021681 is a prime.

It is a super-2 number, since 2×781021681² = 1219989732384131522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (781021687) 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 7 ways as a sum of consecutive naturals, for example, 65046 + ... + 76111.

It is an arithmetic number, because the mean of its divisors is an integer number (106715448).

Almost surely, 2^781021681 is an apocalyptic number.

It is an amenable number.

781021681 is a deficient number, since it is larger than the sum of its proper divisors (72701903).

781021681 is a wasteful number, since it uses less digits than its factorization.

781021681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141671.

The product of its (nonzero) digits is 5376, while the sum is 34.

The square root of 781021681 is about 27946.7651258603. The cubic root of 781021681 is about 920.9181449170.

The spelling of 781021681 in words is "seven hundred eighty-one million, twenty-one thousand, six hundred eighty-one".