21207795840 has 1728 divisors, whose sum is σ = 101328252480. Its totient is φ = 4215214080.

The previous prime is 21207795811. The next prime is 21207795871. The reversal of 21207795840 is 4859770212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (1728).

It is a super-2 number, since 2×21207795840² (a number of 21 digits) contains 22 as substring.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 922078069 + ... + 922078091.

It is an arithmetic number, because the mean of its divisors is an integer number (58639035).

Almost surely, 2^21207795840 is an apocalyptic number.

21207795840 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 21207795840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (50664126240).

21207795840 is an abundant number, since it is smaller than the sum of its proper divisors (80120456640).

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

21207795840 is a wasteful number, since it uses less digits than its factorization.

21207795840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93 (or 51 counting only the distinct ones).

The product of its (nonzero) digits is 282240, while the sum is 45.

The spelling of 21207795840 in words is "twenty-one billion, two hundred seven million, seven hundred ninety-five thousand, eight hundred forty".