3990913781 has 4 divisors (see below), whose sum is σ = 4016333772. Its totient is φ = 3965493792.

The previous prime is 3990913753. The next prime is 3990913783. The reversal of 3990913781 is 1873190993.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1873190993 = 4261 ⋅439613.

It can be written as a sum of positive squares in 2 ways, for example, as 1113556900 + 2877356881 = 33370^2 + 53641^2 .

It is a cyclic number.

It is not a de Polignac number, because 3990913781 - 2¹⁴ = 3990897397 is a prime.

It is a super-2 number, since 2×3990913781² = 31854785614751431922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3990913783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12709760 + ... + 12710073.

It is an arithmetic number, because the mean of its divisors is an integer number (1004083443).

Almost surely, 2^3990913781 is an apocalyptic number.

It is an amenable number.

3990913781 is a deficient number, since it is larger than the sum of its proper divisors (25419991).

3990913781 is a wasteful number, since it uses less digits than its factorization.

3990913781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25419990.

The product of its (nonzero) digits is 367416, while the sum is 50.

The square root of 3990913781 is about 63173.6794954988. The cubic root of 3990913781 is about 1586.1981845816.

The spelling of 3990913781 in words is "three billion, nine hundred ninety million, nine hundred thirteen thousand, seven hundred eighty-one".