3921791681 has 4 divisors (see below), whose sum is σ = 3921924864. Its totient is φ = 3921658500.

The previous prime is 3921791677. The next prime is 3921791683. The reversal of 3921791681 is 1861971293.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 3921791681 - 2² = 3921791677 is a prime.

It is a super-2 number, since 2×3921791681² = 30760899978321611522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3921791683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 665 + ... + 88566.

It is an arithmetic number, because the mean of its divisors is an integer number (980481216).

Almost surely, 2^3921791681 is an apocalyptic number.

It is an amenable number.

3921791681 is a deficient number, since it is larger than the sum of its proper divisors (133183).

3921791681 is an equidigital number, since it uses as much as digits as its factorization.

3921791681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133182.

The product of its digits is 163296, while the sum is 47.

The square root of 3921791681 is about 62624.2100229616. The cubic root of 3921791681 is about 1576.9872194753.

The spelling of 3921791681 in words is "three billion, nine hundred twenty-one million, seven hundred ninety-one thousand, six hundred eighty-one".