20915971 has 4 divisors (see below), whose sum is σ = 21033000. Its totient is φ = 20798944.

The previous prime is 20915969. The next prime is 20915981. The reversal of 20915971 is 17951902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17951902 = 2 ⋅8975951.

It is a cyclic number.

It is not a de Polignac number, because 20915971 - 2¹ = 20915969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20915911) by changing a digit.

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, 58246 + ... + 58603.

It is an arithmetic number, because the mean of its divisors is an integer number (5258250).

Almost surely, 2^20915971 is an apocalyptic number.

20915971 is a deficient number, since it is larger than the sum of its proper divisors (117029).

20915971 is a wasteful number, since it uses less digits than its factorization.

20915971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117028.

The product of its (nonzero) digits is 5670, while the sum is 34.

The square root of 20915971 is about 4573.3981895304. The cubic root of 20915971 is about 275.5239421750.

The spelling of 20915971 in words is "twenty million, nine hundred fifteen thousand, nine hundred seventy-one".