20707991 has 2 divisors, whose sum is σ = 20707992. Its totient is φ = 20707990.

The previous prime is 20707987. The next prime is 20708011. The reversal of 20707991 is 19970702.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20707991 - 2² = 20707987 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 (20701991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10353995 + 10353996.

It is an arithmetic number, because the mean of its divisors is an integer number (10353996).

Almost surely, 2^20707991 is an apocalyptic number.

20707991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20707991 is an equidigital number, since it uses as much as digits as its factorization.

20707991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7938, while the sum is 35.

The square root of 20707991 is about 4550.6033665878. The cubic root of 20707991 is about 274.6076653269.

The spelling of 20707991 in words is "twenty million, seven hundred seven thousand, nine hundred ninety-one".