20645709840 has 640 divisors, whose sum is σ = 88862883840. Its totient is φ = 4296499200.

The previous prime is 20645709827. The next prime is 20645709863. The reversal of 20645709840 is 4890754602.

It is a happy number.

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

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 7966945 + ... + 7969535.

It is an arithmetic number, because the mean of its divisors is an integer number (138848256).

Almost surely, 2^20645709840 is an apocalyptic number.

20645709840 is a gapful number since it is divisible by the number (20) 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 20645709840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44431441920).

20645709840 is an abundant number, since it is smaller than the sum of its proper divisors (68217174000).

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

20645709840 is a wasteful number, since it uses less digits than its factorization.

20645709840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2668 (or 2656 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 20645709840 in words is "twenty billion, six hundred forty-five million, seven hundred nine thousand, eight hundred forty".