39640021 has 4 divisors (see below), whose sum is σ = 39678444. Its totient is φ = 39601600.

The previous prime is 39640001. The next prime is 39640043. The reversal of 39640021 is 12004693.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12004693 = 47 ⋅255419.

It can be written as a sum of positive squares in 2 ways, for example, as 26780625 + 12859396 = 5175^2 + 3586^2 .

It is a cyclic number.

It is not a de Polignac number, because 39640021 - 2⁷ = 39639893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (39640001) 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, 17620 + ... + 19741.

It is an arithmetic number, because the mean of its divisors is an integer number (9919611).

Almost surely, 2^39640021 is an apocalyptic number.

It is an amenable number.

39640021 is a deficient number, since it is larger than the sum of its proper divisors (38423).

39640021 is a wasteful number, since it uses less digits than its factorization.

39640021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38422.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 39640021 is about 6296.0321631961. The cubic root of 39640021 is about 340.9661705389.

The spelling of 39640021 in words is "thirty-nine million, six hundred forty thousand, twenty-one".