1681821626 has 4 divisors (see below), whose sum is σ = 2522732442. Its totient is φ = 840910812.

The previous prime is 1681821607. The next prime is 1681821629. The reversal of 1681821626 is 6261281861.

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

It can be written as a sum of positive squares in only one way, i.e., 1159470601 + 522351025 = 34051^2 + 22855^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1681821629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 420455405 + ... + 420455408.

Almost surely, 2^1681821626 is an apocalyptic number.

1681821626 is a deficient number, since it is larger than the sum of its proper divisors (840910816).

1681821626 is an equidigital number, since it uses as much as digits as its factorization.

1681821626 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840910815.

The product of its digits is 55296, while the sum is 41.

The square root of 1681821626 is about 41010.0186052140. The cubic root of 1681821626 is about 1189.2139021267.

The spelling of 1681821626 in words is "one billion, six hundred eighty-one million, eight hundred twenty-one thousand, six hundred twenty-six".