39721838021 has 2 divisors, whose sum is σ = 39721838022. Its totient is φ = 39721838020.

The previous prime is 39721837957. The next prime is 39721838081. The reversal of 39721838021 is 12083812793.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27084930625 + 12636907396 = 164575^2 + 112414^2 .

It is a cyclic number.

It is not a de Polignac number, because 39721838021 - 2⁶ = 39721837957 is a prime.

It is a super-2 number, since 2×39721838021² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (39721838081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19860919010 + 19860919011.

It is an arithmetic number, because the mean of its divisors is an integer number (19860919011).

Almost surely, 2^39721838021 is an apocalyptic number.

It is an amenable number.

39721838021 is a deficient number, since it is larger than the sum of its proper divisors (1).

39721838021 is an equidigital number, since it uses as much as digits as its factorization.

39721838021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 145152, while the sum is 44.

The spelling of 39721838021 in words is "thirty-nine billion, seven hundred twenty-one million, eight hundred thirty-eight thousand, twenty-one".