20407721 has 2 divisors, whose sum is σ = 20407722. Its totient is φ = 20407720.

The previous prime is 20407711. The next prime is 20407727. The reversal of 20407721 is 12770402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16933225 + 3474496 = 4115^2 + 1864^2 .

It is a cyclic number.

It is not a de Polignac number, because 20407721 - 2¹⁰ = 20406697 is a prime.

It is not a weakly prime, because it can be changed into another prime (20407727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10203860 + 10203861.

It is an arithmetic number, because the mean of its divisors is an integer number (10203861).

Almost surely, 2^20407721 is an apocalyptic number.

It is an amenable number.

20407721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20407721 is an equidigital number, since it uses as much as digits as its factorization.

20407721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 20407721 is about 4517.4905644616. The cubic root of 20407721 is about 273.2739091850.

The spelling of 20407721 in words is "twenty million, four hundred seven thousand, seven hundred twenty-one".