20971999 has 4 divisors (see below), whose sum is σ = 22205664. Its totient is φ = 19738336.

The previous prime is 20971997. The next prime is 20972023. The reversal of 20971999 is 99917902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20971999 - 2¹ = 20971997 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 (20971997) 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, 616807 + ... + 616840.

It is an arithmetic number, because the mean of its divisors is an integer number (5551416).

Almost surely, 2^20971999 is an apocalyptic number.

20971999 is a deficient number, since it is larger than the sum of its proper divisors (1233665).

20971999 is a wasteful number, since it uses less digits than its factorization.

20971999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1233664.

The product of its (nonzero) digits is 91854, while the sum is 46.

The square root of 20971999 is about 4579.5195162812. The cubic root of 20971999 is about 275.7697398650.

It can be divided in two parts, 2097 and 1999, that added together give a 12-th power (4096 = 2¹²).

The spelling of 20971999 in words is "twenty million, nine hundred seventy-one thousand, nine hundred ninety-nine".