19722721 has 2 divisors, whose sum is σ = 19722722. Its totient is φ = 19722720.

The previous prime is 19722713. The next prime is 19722761. The reversal of 19722721 is 12722791.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16900321 + 2822400 = 4111^2 + 1680^2 .

It is an emirp because it is prime and its reverse (12722791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19722721 - 2³ = 19722713 is a prime.

It is not a weakly prime, because it can be changed into another prime (19722701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9861360 + 9861361.

It is an arithmetic number, because the mean of its divisors is an integer number (9861361).

Almost surely, 2^19722721 is an apocalyptic number.

It is an amenable number.

19722721 is a deficient number, since it is larger than the sum of its proper divisors (1).

19722721 is an equidigital number, since it uses as much as digits as its factorization.

19722721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3528, while the sum is 31.

The square root of 19722721 is about 4441.0270208590. The cubic root of 19722721 is about 270.1815011909.

The spelling of 19722721 in words is "nineteen million, seven hundred twenty-two thousand, seven hundred twenty-one".