38691721 has 2 divisors, whose sum is σ = 38691722. Its totient is φ = 38691720.

The previous prime is 38691691. The next prime is 38691743. The reversal of 38691721 is 12719683.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20748025 + 17943696 = 4555^2 + 4236^2 .

It is a cyclic number.

It is not a de Polignac number, because 38691721 - 2⁹ = 38691209 is a prime.

It is not a weakly prime, because it can be changed into another prime (38691761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19345860 + 19345861.

It is an arithmetic number, because the mean of its divisors is an integer number (19345861).

Almost surely, 2^38691721 is an apocalyptic number.

It is an amenable number.

38691721 is a deficient number, since it is larger than the sum of its proper divisors (1).

38691721 is an equidigital number, since it uses as much as digits as its factorization.

38691721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 38691721 is about 6220.2669556861. The cubic root of 38691721 is about 338.2252417179.

The spelling of 38691721 in words is "thirty-eight million, six hundred ninety-one thousand, seven hundred twenty-one".