20639646720 has 1056 divisors, whose sum is σ = 93417874560. Its totient is φ = 4273274880.

The previous prime is 20639646707. The next prime is 20639646757. The reversal of 20639646720 is 2764693602.

20639646720 is a `hidden beast` number, since 2 + 0 + 639 + 6 + 4 + 6 + 7 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1056).

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 95 ways as a sum of consecutive naturals, for example, 74511222 + ... + 74511498.

Almost surely, 2^20639646720 is an apocalyptic number.

20639646720 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 20639646720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46708937280).

20639646720 is an abundant number, since it is smaller than the sum of its proper divisors (72778227840).

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

20639646720 is a wasteful number, since it uses less digits than its factorization.

20639646720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 336 (or 305 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 45.

It can be divided in two parts, 206396 and 46720, that added together give a triangular number (253116 = T₇₁₁).

The spelling of 20639646720 in words is "twenty billion, six hundred thirty-nine million, six hundred forty-six thousand, seven hundred twenty".