681387840 has 336 divisors, whose sum is σ = 2721059328. Its totient is φ = 153280512.

The previous prime is 681387809. The next prime is 681387887. The reversal of 681387840 is 48783186.

It is a tau number, because it is divible by the number of its divisors (336).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1471449 + ... + 1471911.

Almost surely, 2^681387840 is an apocalyptic number.

681387840 is a gapful number since it is divisible by the number (60) 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 681387840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1360529664).

681387840 is an abundant number, since it is smaller than the sum of its proper divisors (2039671488).

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

681387840 is a wasteful number, since it uses less digits than its factorization.

681387840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 566 (or 553 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 45.

The square root of 681387840 is about 26103.4066742255. The cubic root of 681387840 is about 879.9637726133.

It can be divided in two parts, 681 and 387840, that added together give a triangular number (388521 = T₈₈₁).

The spelling of 681387840 in words is "six hundred eighty-one million, three hundred eighty-seven thousand, eight hundred forty".