19975721 has 2 divisors, whose sum is σ = 19975722. Its totient is φ = 19975720.

The previous prime is 19975699. The next prime is 19975727. The reversal of 19975721 is 12757991.

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., 19044496 + 931225 = 4364^2 + 965^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19975721 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19975727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9987860 + 9987861.

It is an arithmetic number, because the mean of its divisors is an integer number (9987861).

Almost surely, 2^19975721 is an apocalyptic number.

It is an amenable number.

19975721 is a deficient number, since it is larger than the sum of its proper divisors (1).

19975721 is an equidigital number, since it uses as much as digits as its factorization.

19975721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39690, while the sum is 41.

The square root of 19975721 is about 4469.4206559687. The cubic root of 19975721 is about 271.3318782743.

The spelling of 19975721 in words is "nineteen million, nine hundred seventy-five thousand, seven hundred twenty-one".