19930991 has 2 divisors, whose sum is σ = 19930992. Its totient is φ = 19930990.

The previous prime is 19930921. The next prime is 19931011. The reversal of 19930991 is 19903991.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 19930991 - 2¹⁴ = 19914607 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19930921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9965495 + 9965496.

It is an arithmetic number, because the mean of its divisors is an integer number (9965496).

Almost surely, 2^19930991 is an apocalyptic number.

19930991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19930991 is an equidigital number, since it uses as much as digits as its factorization.

19930991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19683, while the sum is 41.

The square root of 19930991 is about 4464.4138473040. The cubic root of 19930991 is about 271.1292031520.

Subtracting from 19930991 its reverse (19903991), we obtain a cube (27000 = 30³).

The spelling of 19930991 in words is "nineteen million, nine hundred thirty thousand, nine hundred ninety-one".