3968397721 has 2 divisors, whose sum is σ = 3968397722. Its totient is φ = 3968397720.

The previous prime is 3968397691. The next prime is 3968397751. The reversal of 3968397721 is 1277938693.

It is a happy number.

3968397721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a balanced prime because it is at equal distance from previous prime (3968397691) and next prime (3968397751).

It can be written as a sum of positive squares in only one way, i.e., 3716731225 + 251666496 = 60965^2 + 15864^2 .

It is an emirp because it is prime and its reverse (1277938693) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-3968397721 is a prime.

It is not a weakly prime, because it can be changed into another prime (3968397751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1984198860 + 1984198861.

It is an arithmetic number, because the mean of its divisors is an integer number (1984198861).

Almost surely, 2^3968397721 is an apocalyptic number.

It is an amenable number.

3968397721 is a deficient number, since it is larger than the sum of its proper divisors (1).

3968397721 is an equidigital number, since it uses as much as digits as its factorization.

3968397721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3429216, while the sum is 55.

The square root of 3968397721 is about 62995.2198265868. The cubic root of 3968397721 is about 1583.2095364803.

The spelling of 3968397721 in words is "three billion, nine hundred sixty-eight million, three hundred ninety-seven thousand, seven hundred twenty-one".