1691828821 has 4 divisors (see below), whose sum is σ = 1691946112. Its totient is φ = 1691711532.

The previous prime is 1691828791. The next prime is 1691828903. The reversal of 1691828821 is 1288281961.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1288281961 = 33461 ⋅38501.

It is a cyclic number.

It is not a de Polignac number, because 1691828821 - 2⁷ = 1691828693 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1691826821) 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, 33381 + ... + 67066.

It is an arithmetic number, because the mean of its divisors is an integer number (422986528).

Almost surely, 2^1691828821 is an apocalyptic number.

It is an amenable number.

1691828821 is a deficient number, since it is larger than the sum of its proper divisors (117291).

1691828821 is a wasteful number, since it uses less digits than its factorization.

1691828821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117290.

The product of its digits is 110592, while the sum is 46.

The square root of 1691828821 is about 41131.8467978281. The cubic root of 1691828821 is about 1191.5679308504.

The spelling of 1691828821 in words is "one billion, six hundred ninety-one million, eight hundred twenty-eight thousand, eight hundred twenty-one".