3931721 has 2 divisors, whose sum is σ = 3931722. Its totient is φ = 3931720.

The previous prime is 3931693. The next prime is 3931729. The reversal of 3931721 is 1271393.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3385600 + 546121 = 1840^2 + 739^2 .

It is an emirp because it is prime and its reverse (1271393) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3931721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (3931729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1965860 + 1965861.

It is an arithmetic number, because the mean of its divisors is an integer number (1965861).

Almost surely, 2^3931721 is an apocalyptic number.

It is an amenable number.

3931721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3931721 is an equidigital number, since it uses as much as digits as its factorization.

3931721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1134, while the sum is 26.

The square root of 3931721 is about 1982.8567774804. The cubic root of 3931721 is about 157.8316986936.

The spelling of 3931721 in words is "three million, nine hundred thirty-one thousand, seven hundred twenty-one".