20473721 has 2 divisors, whose sum is σ = 20473722. Its totient is φ = 20473720.

The previous prime is 20473709. The next prime is 20473723. The reversal of 20473721 is 12737402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17106496 + 3367225 = 4136^2 + 1835^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20473721 is a prime.

It is a Sophie Germain prime.

Together with 20473723, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20473723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10236860 + 10236861.

It is an arithmetic number, because the mean of its divisors is an integer number (10236861).

Almost surely, 2^20473721 is an apocalyptic number.

It is an amenable number.

20473721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20473721 is an equidigital number, since it uses as much as digits as its factorization.

20473721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 20473721 is about 4524.7896083685. The cubic root of 20473721 is about 273.5681878317.

The spelling of 20473721 in words is "twenty million, four hundred seventy-three thousand, seven hundred twenty-one".