20921723 has 2 divisors, whose sum is σ = 20921724. Its totient is φ = 20921722.

The previous prime is 20921711. The next prime is 20921729. The reversal of 20921723 is 32712902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20921723 - 2⁴ = 20921707 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20921692 and 20921701.

It is not a weakly prime, because it can be changed into another prime (20921729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10460861 + 10460862.

It is an arithmetic number, because the mean of its divisors is an integer number (10460862).

Almost surely, 2^20921723 is an apocalyptic number.

20921723 is a deficient number, since it is larger than the sum of its proper divisors (1).

20921723 is an equidigital number, since it uses as much as digits as its factorization.

20921723 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 20921723 is about 4574.0270003576. The cubic root of 20921723 is about 275.5491966956.

The spelling of 20921723 in words is "twenty million, nine hundred twenty-one thousand, seven hundred twenty-three".