21509767840 has 48 divisors (see below), whose sum is σ = 55436542560. Its totient is φ = 7821733120.

The previous prime is 21509767801. The next prime is 21509767841. The reversal of 21509767840 is 4876790512.

It is a super-2 number, since 2×21509767840² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21509767841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6108970 + ... + 6112489.

It is an arithmetic number, because the mean of its divisors is an integer number (1154927970).

Almost surely, 2^21509767840 is an apocalyptic number.

21509767840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21509767840 is an abundant number, since it is smaller than the sum of its proper divisors (33926774720).

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

21509767840 is a wasteful number, since it uses less digits than its factorization.

21509767840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12221485 (or 12221477 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 49.

The spelling of 21509767840 in words is "twenty-one billion, five hundred nine million, seven hundred sixty-seven thousand, eight hundred forty".