1681245720 has 640 divisors, whose sum is σ = 7376624640. Its totient is φ = 333020160.

The previous prime is 1681245703. The next prime is 1681245749. The reversal of 1681245720 is 275421861.

1681245720 is a `hidden beast` number, since 1 + 6 + 81 + 2 + 4 + 572 + 0 = 666.

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

It is a congruent number.

It is an unprimeable number.

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 159 ways as a sum of consecutive naturals, for example, 5737894 + ... + 5738186.

It is an arithmetic number, because the mean of its divisors is an integer number (11525976).

Almost surely, 2^1681245720 is an apocalyptic number.

1681245720 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 1681245720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3688312320).

1681245720 is an abundant number, since it is smaller than the sum of its proper divisors (5695378920).

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

1681245720 is a wasteful number, since it uses less digits than its factorization.

1681245720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 357 (or 344 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 1681245720 is about 41002.9964758675. The cubic root of 1681245720 is about 1189.0781458333.

The spelling of 1681245720 in words is "one billion, six hundred eighty-one million, two hundred forty-five thousand, seven hundred twenty".