20446721 has 2 divisors, whose sum is σ = 20446722. Its totient is φ = 20446720.

The previous prime is 20446709. The next prime is 20446729. The reversal of 20446721 is 12764402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18181696 + 2265025 = 4264^2 + 1505^2 .

It is a cyclic number.

It is not a de Polignac number, because 20446721 - 2¹⁰ = 20445697 is a prime.

It is not a weakly prime, because it can be changed into another prime (20446729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10223360 + 10223361.

It is an arithmetic number, because the mean of its divisors is an integer number (10223361).

Almost surely, 2^20446721 is an apocalyptic number.

It is an amenable number.

20446721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20446721 is an equidigital number, since it uses as much as digits as its factorization.

20446721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 20446721 is about 4521.8050599291. The cubic root of 20446721 is about 273.4478776644.

The spelling of 20446721 in words is "twenty million, four hundred forty-six thousand, seven hundred twenty-one".