20519921 has 2 divisors, whose sum is σ = 20519922. Its totient is φ = 20519920.

The previous prime is 20519911. The next prime is 20519927. The reversal of 20519921 is 12991502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19936225 + 583696 = 4465^2 + 764^2 .

It is a cyclic number.

It is not a de Polignac number, because 20519921 - 2⁶ = 20519857 is a prime.

It is not a weakly prime, because it can be changed into another prime (20519927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10259960 + 10259961.

It is an arithmetic number, because the mean of its divisors is an integer number (10259961).

Almost surely, 2^20519921 is an apocalyptic number.

It is an amenable number.

20519921 is a deficient number, since it is larger than the sum of its proper divisors (1).

20519921 is an equidigital number, since it uses as much as digits as its factorization.

20519921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1620, while the sum is 29.

The square root of 20519921 is about 4529.8919413160. The cubic root of 20519921 is about 273.7738067882.

The spelling of 20519921 in words is "twenty million, five hundred nineteen thousand, nine hundred twenty-one".