21051566040 has 256 divisors, whose sum is σ = 70516915200. Its totient is φ = 5002905600.

The previous prime is 21051566033. The next prime is 21051566051. The reversal of 21051566040 is 4066515012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21051565989 and 21051566007.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3195550 + ... + 3202130.

It is an arithmetic number, because the mean of its divisors is an integer number (275456700).

Almost surely, 2^21051566040 is an apocalyptic number.

21051566040 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 21051566040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35258457600).

21051566040 is an abundant number, since it is smaller than the sum of its proper divisors (49465349160).

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

21051566040 is a wasteful number, since it uses less digits than its factorization.

21051566040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6698 (or 6694 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 30.

The spelling of 21051566040 in words is "twenty-one billion, fifty-one million, five hundred sixty-six thousand, forty".