3971319921 has 20 divisors (see below), whose sum is σ = 5941013364. Its totient is φ = 2643732000.

The previous prime is 3971319917. The next prime is 3971319923. The reversal of 3971319921 is 1299131793.

3971319921 is digitally balanced in base 2 and base 4, because in such bases it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 1881824400 + 2089495521 = 43380^2 + 45711^2 .

It is not a de Polignac number, because 3971319921 - 2² = 3971319917 is a prime.

It is not an unprimeable number, because it can be changed into a prime (3971319923) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 21811 + ... + 91751.

Almost surely, 2^3971319921 is an apocalyptic number.

It is an amenable number.

3971319921 is a deficient number, since it is larger than the sum of its proper divisors (1969693443).

3971319921 is an equidigital number, since it uses as much as digits as its factorization.

3971319921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70654 (or 70645 counting only the distinct ones).

The product of its digits is 91854, while the sum is 45.

The square root of 3971319921 is about 63018.4093817037. The cubic root of 3971319921 is about 1583.5980492678.

The spelling of 3971319921 in words is "three billion, nine hundred seventy-one million, three hundred nineteen thousand, nine hundred twenty-one".