39991621 has 4 divisors (see below), whose sum is σ = 40070700. Its totient is φ = 39912544.

The previous prime is 39991619. The next prime is 39991669. The reversal of 39991621 is 12619993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12619993 = 727 ⋅17359.

It can be written as a sum of positive squares in 2 ways, for example, as 37149025 + 2842596 = 6095^2 + 1686^2 .

It is a cyclic number.

It is not a de Polignac number, because 39991621 - 2¹ = 39991619 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 (39991681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38776 + ... + 39793.

It is an arithmetic number, because the mean of its divisors is an integer number (10017675).

Almost surely, 2^39991621 is an apocalyptic number.

It is an amenable number.

39991621 is a deficient number, since it is larger than the sum of its proper divisors (79079).

39991621 is an equidigital number, since it uses as much as digits as its factorization.

39991621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79078.

The product of its digits is 26244, while the sum is 40.

The square root of 39991621 is about 6323.8928675303. The cubic root of 39991621 is about 341.9713078536.

The spelling of 39991621 in words is "thirty-nine million, nine hundred ninety-one thousand, six hundred twenty-one".