28721891520 has 224 divisors, whose sum is σ = 115799616000. Its totient is φ = 6564989952.

The previous prime is 28721891509. The next prime is 28721891521. The reversal of 28721891520 is 2519812782.

28721891520 is a `hidden beast` number, since 28 + 7 + 2 + 18 + 91 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (224).

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

It is not an unprimeable number, because it can be changed into a prime (28721891521) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 176970 + ... + 297929.

Almost surely, 2^28721891520 is an apocalyptic number.

28721891520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28721891520 is an abundant number, since it is smaller than the sum of its proper divisors (87077724480).

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

28721891520 is a wasteful number, since it uses less digits than its factorization.

28721891520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 474932 (or 474916 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 45.

The spelling of 28721891520 in words is "twenty-eight billion, seven hundred twenty-one million, eight hundred ninety-one thousand, five hundred twenty".