39721397 has 2 divisors, whose sum is σ = 39721398. Its totient is φ = 39721396.

The previous prime is 39721373. The next prime is 39721399. The reversal of 39721397 is 79312793.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20016676 + 19704721 = 4474^2 + 4439^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-39721397 is a prime.

Together with 39721399, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (39721399) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19860698 + 19860699.

It is an arithmetic number, because the mean of its divisors is an integer number (19860699).

Almost surely, 2^39721397 is an apocalyptic number.

It is an amenable number.

39721397 is a deficient number, since it is larger than the sum of its proper divisors (1).

39721397 is an equidigital number, since it uses as much as digits as its factorization.

39721397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 71442, while the sum is 41.

The square root of 39721397 is about 6302.4913327985. The cubic root of 39721397 is about 341.1993313474.

The spelling of 39721397 in words is "thirty-nine million, seven hundred twenty-one thousand, three hundred ninety-seven".