19711921 has 2 divisors, whose sum is σ = 19711922. Its totient is φ = 19711920.

The previous prime is 19711907. The next prime is 19711927. The reversal of 19711921 is 12911791.

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., 14137600 + 5574321 = 3760^2 + 2361^2 .

It is a cyclic number.

It is not a de Polignac number, because 19711921 - 2⁵ = 19711889 is a prime.

It is not a weakly prime, because it can be changed into another prime (19711927) 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, 9855960 + 9855961.

It is an arithmetic number, because the mean of its divisors is an integer number (9855961).

Almost surely, 2^19711921 is an apocalyptic number.

It is an amenable number.

19711921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19711921 is an equidigital number, since it uses as much as digits as its factorization.

19711921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1134, while the sum is 31.

The square root of 19711921 is about 4439.8109193974. The cubic root of 19711921 is about 270.1321757962.

The spelling of 19711921 in words is "nineteen million, seven hundred eleven thousand, nine hundred twenty-one".