20297721 has 8 divisors (see below), whose sum is σ = 27096480. Its totient is φ = 13515392.

The previous prime is 20297713. The next prime is 20297731. The reversal of 20297721 is 12779202.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20297721 - 2³ = 20297713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20297731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 855 + ... + 6428.

It is an arithmetic number, because the mean of its divisors is an integer number (3387060).

Almost surely, 2^20297721 is an apocalyptic number.

It is an amenable number.

20297721 is a deficient number, since it is larger than the sum of its proper divisors (6798759).

20297721 is an equidigital number, since it uses as much as digits as its factorization.

20297721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8215.

The product of its (nonzero) digits is 3528, while the sum is 30.

The square root of 20297721 is about 4505.2992131489. The cubic root of 20297721 is about 272.7820316006.

The spelling of 20297721 in words is "twenty million, two hundred ninety-seven thousand, seven hundred twenty-one".