1681721764 has 24 divisors (see below), whose sum is σ = 3051141408. Its totient is φ = 810461760.

The previous prime is 1681721761. The next prime is 1681721771. The reversal of 1681721764 is 4671271861.

It is a super-2 number, since 2×1681721764² = 5656376183022543392, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1681721764.

It is not an unprimeable number, because it can be changed into a prime (1681721761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48162 + ... + 75385.

It is an arithmetic number, because the mean of its divisors is an integer number (127130892).

Almost surely, 2^1681721764 is an apocalyptic number.

It is an amenable number.

1681721764 is a deficient number, since it is larger than the sum of its proper divisors (1369419644).

1681721764 is a wasteful number, since it uses less digits than its factorization.

1681721764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123675 (or 123673 counting only the distinct ones).

The product of its digits is 112896, while the sum is 43.

The square root of 1681721764 is about 41008.8010553832. The cubic root of 1681721764 is about 1189.1903642303.

The spelling of 1681721764 in words is "one billion, six hundred eighty-one million, seven hundred twenty-one thousand, seven hundred sixty-four".