1991428 has 12 divisors (see below), whose sum is σ = 3668560. Its totient is φ = 943272.

The previous prime is 1991413. The next prime is 1991443. The reversal of 1991428 is 8241991.

It is an interprime number because it is at equal distance from previous prime (1991413) and next prime (1991443).

It is a junction number, because it is equal to n+sod(n) for n = 1991393 and 1991402.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13026 + ... + 13177.

2^1991428 is an apocalyptic number.

It is an amenable number.

1991428 is a deficient number, since it is larger than the sum of its proper divisors (1677132).

1991428 is a wasteful number, since it uses less digits than its factorization.

1991428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26226 (or 26224 counting only the distinct ones).

The product of its digits is 5184, while the sum is 34.

The square root of 1991428 is about 1411.1796483793. The cubic root of 1991428 is about 125.8118464937.

The spelling of 1991428 in words is "one million, nine hundred ninety-one thousand, four hundred twenty-eight".