21765804081 has 8 divisors (see below), whose sum is σ = 33166939584. Its totient is φ = 12437602320.

The previous prime is 21765804059. The next prime is 21765804083. The reversal of 21765804081 is 18040856712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21765804081 - 2⁶ = 21765804017 is a prime.

It is a super-2 number, since 2×21765804081² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21765804083) 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, 518233410 + ... + 518233451.

It is an arithmetic number, because the mean of its divisors is an integer number (4145867448).

Almost surely, 2^21765804081 is an apocalyptic number.

21765804081 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21765804081 is a deficient number, since it is larger than the sum of its proper divisors (11401135503).

21765804081 is a wasteful number, since it uses less digits than its factorization.

21765804081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1036466871.

The product of its (nonzero) digits is 107520, while the sum is 42.

The spelling of 21765804081 in words is "twenty-one billion, seven hundred sixty-five million, eight hundred four thousand, eighty-one".