1321991 has 4 divisors (see below), whose sum is σ = 1442184. Its totient is φ = 1201800.

The previous prime is 1321981. The next prime is 1321997. The reversal of 1321991 is 1991231.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1321991 - 2⁶ = 1321927 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1321991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1321997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60080 + ... + 60101.

It is an arithmetic number, because the mean of its divisors is an integer number (360546).

2^1321991 is an apocalyptic number.

1321991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1321991 is a deficient number, since it is larger than the sum of its proper divisors (120193).

1321991 is a wasteful number, since it uses less digits than its factorization.

1321991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120192.

The product of its digits is 486, while the sum is 26.

The square root of 1321991 is about 1149.7786743543. The cubic root of 1321991 is about 109.7512561193.

The spelling of 1321991 in words is "one million, three hundred twenty-one thousand, nine hundred ninety-one".