21138542880 has 768 divisors, whose sum is σ = 86227255296. Its totient is φ = 4233461760.

The previous prime is 21138542861. The next prime is 21138542923. The reversal of 21138542880 is 8824583112.

It is a Cunningham number, because it is equal to 145391²-1.

It is a Harshad number since it is a multiple of its sum of digits (42).

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, 90723244 + ... + 90723476.

It is an arithmetic number, because the mean of its divisors is an integer number (112275072).

Almost surely, 2^21138542880 is an apocalyptic number.

21138542880 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 21138542880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43113627648).

21138542880 is an abundant number, since it is smaller than the sum of its proper divisors (65088712416).

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

21138542880 is a wasteful number, since it uses less digits than its factorization.

21138542880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 369 (or 361 counting only the distinct ones).

The product of its (nonzero) digits is 122880, while the sum is 42.

The spelling of 21138542880 in words is "twenty-one billion, one hundred thirty-eight million, five hundred forty-two thousand, eight hundred eighty".