1023991 has 2 divisors, whose sum is σ = 1023992. Its totient is φ = 1023990.

The previous prime is 1023977. The next prime is 1024021. The reversal of 1023991 is 1993201.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1023991 - 2¹⁵ = 991223 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1023941) 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, 511995 + 511996.

It is an arithmetic number, because the mean of its divisors is an integer number (511996).

2^1023991 is an apocalyptic number.

1023991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1023991 is an equidigital number, since it uses as much as digits as its factorization.

1023991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 1023991 is about 1011.9244042912. The cubic root of 1023991 is about 100.7933886967.

It can be divided in two parts, 102399 and 1, that added together give a square (102400 = 320²).

The spelling of 1023991 in words is "one million, twenty-three thousand, nine hundred ninety-one".