20896721 has 2 divisors, whose sum is σ = 20896722. Its totient is φ = 20896720.

The previous prime is 20896693. The next prime is 20896741. The reversal of 20896721 is 12769802.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 547600 = 4511^2 + 740^2 .

It is a cyclic number.

It is not a de Polignac number, because 20896721 - 2⁶ = 20896657 is a prime.

It is not a weakly prime, because it can be changed into another prime (20896741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10448360 + 10448361.

It is an arithmetic number, because the mean of its divisors is an integer number (10448361).

Almost surely, 2^20896721 is an apocalyptic number.

It is an amenable number.

20896721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20896721 is an equidigital number, since it uses as much as digits as its factorization.

20896721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 20896721 is about 4571.2931430833. The cubic root of 20896721 is about 275.4393901383.

The spelling of 20896721 in words is "twenty million, eight hundred ninety-six thousand, seven hundred twenty-one".