3961681921 has 8 divisors (see below), whose sum is σ = 4330036224. Its totient is φ = 3608362560.

The previous prime is 3961681907. The next prime is 3961681931. The reversal of 3961681921 is 1291861693.

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

It is a cyclic number.

It is not a de Polignac number, because 3961681921 - 2³¹ = 1814198273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (3961681901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3758185 + ... + 3759238.

It is an arithmetic number, because the mean of its divisors is an integer number (541254528).

Almost surely, 2^3961681921 is an apocalyptic number.

3961681921 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

It is an amenable number.

3961681921 is a deficient number, since it is larger than the sum of its proper divisors (368354303).

3961681921 is a wasteful number, since it uses less digits than its factorization.

3961681921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7517471.

The product of its digits is 139968, while the sum is 46.

The square root of 3961681921 is about 62941.8932111197. The cubic root of 3961681921 is about 1582.3159329931.

The spelling of 3961681921 in words is "three billion, nine hundred sixty-one million, six hundred eighty-one thousand, nine hundred twenty-one".