20939915 has 4 divisors (see below), whose sum is σ = 25127904. Its totient is φ = 16751928.

The previous prime is 20939879. The next prime is 20939927. The reversal of 20939915 is 51993902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 51993902 = 2 ⋅25996951.

It is a cyclic number.

It is not a de Polignac number, because 20939915 - 2¹⁶ = 20874379 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2093987 + ... + 2093996.

It is an arithmetic number, because the mean of its divisors is an integer number (6281976).

Almost surely, 2^20939915 is an apocalyptic number.

20939915 is a deficient number, since it is larger than the sum of its proper divisors (4187989).

20939915 is an equidigital number, since it uses as much as digits as its factorization.

20939915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4187988.

The product of its (nonzero) digits is 21870, while the sum is 38.

The square root of 20939915 is about 4576.0151879119. The cubic root of 20939915 is about 275.6290393671.

The spelling of 20939915 in words is "twenty million, nine hundred thirty-nine thousand, nine hundred fifteen".