686906640 has 240 divisors, whose sum is σ = 2673959808. Its totient is φ = 154773504.

The previous prime is 686906621. The next prime is 686906657. The reversal of 686906640 is 46609686.

It is a tau number, because it is divible by the number of its divisors (240).

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

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 47 ways as a sum of consecutive naturals, for example, 366987 + ... + 368853.

Almost surely, 2^686906640 is an apocalyptic number.

686906640 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 686906640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1336979904).

686906640 is an abundant number, since it is smaller than the sum of its proper divisors (1987053168).

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

686906640 is a wasteful number, since it uses less digits than its factorization.

686906640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1966 (or 1957 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 686906640 is about 26208.9038305687. The cubic root of 686906640 is about 882.3330995381. Note that the first 3 decimals are identical.

The spelling of 686906640 in words is "six hundred eighty-six million, nine hundred six thousand, six hundred forty".