20681971 has 4 divisors (see below), whose sum is σ = 20697712. Its totient is φ = 20666232.

The previous prime is 20681957. The next prime is 20681993. The reversal of 20681971 is 17918602.

It is a happy number.

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 20681971 - 2⁵ = 20681939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20681951) 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, 5700 + ... + 8593.

It is an arithmetic number, because the mean of its divisors is an integer number (5174428).

Almost surely, 2^20681971 is an apocalyptic number.

20681971 is a deficient number, since it is larger than the sum of its proper divisors (15741).

20681971 is a wasteful number, since it uses less digits than its factorization.

20681971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15740.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 20681971 is about 4547.7435063996. The cubic root of 20681971 is about 274.4926004665.

The spelling of 20681971 in words is "twenty million, six hundred eighty-one thousand, nine hundred seventy-one".