19911321 has 12 divisors (see below), whose sum is σ = 28889380. Its totient is φ = 13214880.

The previous prime is 19911319. The next prime is 19911323. The reversal of 19911321 is 12311991.

It is an interprime number because it is at equal distance from previous prime (19911319) and next prime (19911323).

It can be written as a sum of positive squares in 2 ways, for example, as 7485696 + 12425625 = 2736^2 + 3525^2 .

It is not a de Polignac number, because 19911321 - 2¹ = 19911319 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19911323) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2770 + ... + 6891.

Almost surely, 2^19911321 is an apocalyptic number.

It is an amenable number.

19911321 is a deficient number, since it is larger than the sum of its proper divisors (8978059).

19911321 is a wasteful number, since it uses less digits than its factorization.

19911321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9896 (or 9893 counting only the distinct ones).

The product of its digits is 486, while the sum is 27.

The square root of 19911321 is about 4462.2103267327. The cubic root of 19911321 is about 271.0399808480.

The spelling of 19911321 in words is "nineteen million, nine hundred eleven thousand, three hundred twenty-one".