39920618921 has 4 divisors (see below), whose sum is σ = 39924267972. Its totient is φ = 39916969872.

The previous prime is 39920618873. The next prime is 39920618929. The reversal of 39920618921 is 12981602993.

It is a happy number.

39920618921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14236069225 + 25684549696 = 119315^2 + 160264^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-39920618921 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 39920618921.

It is not an unprimeable number, because it can be changed into a prime (39920618929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1808066 + ... + 1830011.

It is an arithmetic number, because the mean of its divisors is an integer number (9981066993).

Almost surely, 2^39920618921 is an apocalyptic number.

It is an amenable number.

39920618921 is a deficient number, since it is larger than the sum of its proper divisors (3649051).

39920618921 is a wasteful number, since it uses less digits than its factorization.

39920618921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3649050.

The product of its (nonzero) digits is 419904, while the sum is 50.

The spelling of 39920618921 in words is "thirty-nine billion, nine hundred twenty million, six hundred eighteen thousand, nine hundred twenty-one".