20581661520 has 320 divisors, whose sum is σ = 81646202880. Its totient is φ = 4668019200.

The previous prime is 20581661501. The next prime is 20581661521. The reversal of 20581661520 is 2516618502.

20581661520 is a `hidden beast` number, since 2 + 0 + 5 + 8 + 16 + 615 + 20 = 666.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20581661521) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1975525 + ... + 1985915.

It is an arithmetic number, because the mean of its divisors is an integer number (255144384).

Almost surely, 2^20581661520 is an apocalyptic number.

20581661520 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 20581661520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40823101440).

20581661520 is an abundant number, since it is smaller than the sum of its proper divisors (61064541360).

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

20581661520 is a wasteful number, since it uses less digits than its factorization.

20581661520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10551 (or 10539 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The spelling of 20581661520 in words is "twenty billion, five hundred eighty-one million, six hundred sixty-one thousand, five hundred twenty".