645761220720 has 1280 divisors, whose sum is σ = 2775154950144. Its totient is φ = 120102912000.

The previous prime is 645761220641. The next prime is 645761220809. The reversal of 645761220720 is 27022167546.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 594076017 + ... + 594077103.

Almost surely, 2^645761220720 is an apocalyptic number.

645761220720 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 645761220720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1387577475072).

645761220720 is an abundant number, since it is smaller than the sum of its proper divisors (2129393729424).

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

645761220720 is a wasteful number, since it uses less digits than its factorization.

645761220720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1230 (or 1224 counting only the distinct ones).

The product of its (nonzero) digits is 282240, while the sum is 42.

The spelling of 645761220720 in words is "six hundred forty-five billion, seven hundred sixty-one million, two hundred twenty thousand, seven hundred twenty".