20071991 has 2 divisors, whose sum is σ = 20071992. Its totient is φ = 20071990.

The previous prime is 20071963. The next prime is 20072027. The reversal of 20071991 is 19917002.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20071991 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 (20071901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10035995 + 10035996.

It is an arithmetic number, because the mean of its divisors is an integer number (10035996).

Almost surely, 2^20071991 is an apocalyptic number.

20071991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20071991 is an equidigital number, since it uses as much as digits as its factorization.

20071991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1134, while the sum is 29.

The square root of 20071991 is about 4480.1775634454. The cubic root of 20071991 is about 271.7670610584.

Adding to 20071991 its reverse (19917002), we get a palindrome (39988993).

The spelling of 20071991 in words is "twenty million, seventy-one thousand, nine hundred ninety-one".