991421 has 4 divisors (see below), whose sum is σ = 1015644. Its totient is φ = 967200.

The previous prime is 991409. The next prime is 991427. The reversal of 991421 is 124199.

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

It can be written as a sum of positive squares in 2 ways, for example, as 343396 + 648025 = 586^2 + 805^2 .

It is a cyclic number.

It is not a de Polignac number, because 991421 - 2⁶ = 991357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12050 + ... + 12131.

It is an arithmetic number, because the mean of its divisors is an integer number (253911).

2⁹⁹¹⁴²¹ is an apocalyptic number.

It is an amenable number.

991421 is a deficient number, since it is larger than the sum of its proper divisors (24223).

991421 is a wasteful number, since it uses less digits than its factorization.

991421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24222.

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

The square root of 991421 is about 995.7012604190. The cubic root of 991421 is about 99.7132116440.

The spelling of 991421 in words is "nine hundred ninety-one thousand, four hundred twenty-one".