20029721 has 2 divisors, whose sum is σ = 20029722. Its totient is φ = 20029720.

The previous prime is 20029693. The next prime is 20029729. The reversal of 20029721 is 12792002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 4096 = 4475^2 + 64^2 .

It is a cyclic number.

It is not a de Polignac number, because 20029721 - 2⁶ = 20029657 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20029729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10014860 + 10014861.

It is an arithmetic number, because the mean of its divisors is an integer number (10014861).

Almost surely, 2^20029721 is an apocalyptic number.

It is an amenable number.

20029721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20029721 is an equidigital number, since it uses as much as digits as its factorization.

20029721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 20029721 is about 4475.4576302318. The cubic root of 20029721 is about 271.5761537870.

The spelling of 20029721 in words is "twenty million, twenty-nine thousand, seven hundred twenty-one".