1681261920 has 480 divisors, whose sum is σ = 6777273888. Its totient is φ = 388841472.

The previous prime is 1681261891. The next prime is 1681261927. The reversal of 1681261920 is 291621861.

1681261920 is a `hidden beast` number, since 1 + 6 + 8 + 12 + 619 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (480).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1681261927) 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 79 ways as a sum of consecutive naturals, for example, 2863867 + ... + 2864453.

Almost surely, 2^1681261920 is an apocalyptic number.

1681261920 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1681261920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3388636944).

1681261920 is an abundant number, since it is smaller than the sum of its proper divisors (5096011968).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1681261920 is a wasteful number, since it uses less digits than its factorization.

1681261920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 644 (or 627 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 36.

The square root of 1681261920 is about 41003.1940219296. The cubic root of 1681261920 is about 1189.0819650260.

The spelling of 1681261920 in words is "one billion, six hundred eighty-one million, two hundred sixty-one thousand, nine hundred twenty".