21516204780 has 288 divisors, whose sum is σ = 76370112000. Its totient is φ = 4901323392.

The previous prime is 21516204779. The next prime is 21516204793. The reversal of 21516204780 is 8740261512.

21516204780 is a `hidden beast` number, since 2 + 1 + 516 + 20 + 47 + 80 = 666.

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

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, 34759311 + ... + 34759929.

It is an arithmetic number, because the mean of its divisors is an integer number (265174000).

Almost surely, 2^21516204780 is an apocalyptic number.

21516204780 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 21516204780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38185056000).

21516204780 is an abundant number, since it is smaller than the sum of its proper divisors (54853907220).

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

21516204780 is a wasteful number, since it uses less digits than its factorization.

21516204780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1218 (or 1199 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The spelling of 21516204780 in words is "twenty-one billion, five hundred sixteen million, two hundred four thousand, seven hundred eighty".