4020001991 has 2 divisors, whose sum is σ = 4020001992. Its totient is φ = 4020001990.

The previous prime is 4020001987. The next prime is 4020002003. The reversal of 4020001991 is 1991000204.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 4020001991 - 2² = 4020001987 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 4020001991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4020001981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2010000995 + 2010000996.

It is an arithmetic number, because the mean of its divisors is an integer number (2010000996).

Almost surely, 2^4020001991 is an apocalyptic number.

4020001991 is a deficient number, since it is larger than the sum of its proper divisors (1).

4020001991 is an equidigital number, since it uses as much as digits as its factorization.

4020001991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 4020001991 is about 63403.4856376209. The cubic root of 4020001991 is about 1590.0425856505.

The spelling of 4020001991 in words is "four billion, twenty million, one thousand, nine hundred ninety-one".