19930721 has 2 divisors, whose sum is σ = 19930722. Its totient is φ = 19930720.

The previous prime is 19930717. The next prime is 19930727. The reversal of 19930721 is 12703991.

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., 11316496 + 8614225 = 3364^2 + 2935^2 .

It is a cyclic number.

It is not a de Polignac number, because 19930721 - 2² = 19930717 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19930727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9965360 + 9965361.

It is an arithmetic number, because the mean of its divisors is an integer number (9965361).

Almost surely, 2^19930721 is an apocalyptic number.

It is an amenable number.

19930721 is a deficient number, since it is larger than the sum of its proper divisors (1).

19930721 is an equidigital number, since it uses as much as digits as its factorization.

19930721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 19930721 is about 4464.3836080695. The cubic root of 19930721 is about 271.1279788407.

The spelling of 19930721 in words is "nineteen million, nine hundred thirty thousand, seven hundred twenty-one".