1991907 has 24 divisors (see below), whose sum is σ = 3122496. Its totient is φ = 1218816.

The previous prime is 1991893. The next prime is 1991911. The reversal of 1991907 is 7091991.

It is not a de Polignac number, because 1991907 - 2⁷ = 1991779 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991947) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7053 + ... + 7329.

It is an arithmetic number, because the mean of its divisors is an integer number (130104).

2^1991907 is an apocalyptic number.

1991907 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

1991907 is a deficient number, since it is larger than the sum of its proper divisors (1130589).

1991907 is a wasteful number, since it uses less digits than its factorization.

1991907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347 (or 344 counting only the distinct ones).

The product of its (nonzero) digits is 5103, while the sum is 36.

The square root of 1991907 is about 1411.3493543414. The cubic root of 1991907 is about 125.8219328979.

The spelling of 1991907 in words is "one million, nine hundred ninety-one thousand, nine hundred seven".