20723971 has 4 divisors (see below), whose sum is σ = 21033352. Its totient is φ = 20414592.

The previous prime is 20723939. The next prime is 20723999. The reversal of 20723971 is 17932702.

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 20723971 - 2⁵ = 20723939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20723921) 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, 154590 + ... + 154723.

It is an arithmetic number, because the mean of its divisors is an integer number (5258338).

Almost surely, 2^20723971 is an apocalyptic number.

20723971 is a deficient number, since it is larger than the sum of its proper divisors (309381).

20723971 is an equidigital number, since it uses as much as digits as its factorization.

20723971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 309380.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 20723971 is about 4552.3588391075. The cubic root of 20723971 is about 274.6782838335.

The spelling of 20723971 in words is "twenty million, seven hundred twenty-three thousand, nine hundred seventy-one".