21221800605 has 16 divisors (see below), whose sum is σ = 37727645760. Its totient is φ = 11318293584.

The previous prime is 21221800601. The next prime is 21221800627. The reversal of 21221800605 is 50600812212.

It is a happy number.

21221800605 is a `hidden beast` number, since 21 + 22 + 18 + 0 + 0 + 605 = 666.

It is not a de Polignac number, because 21221800605 - 2² = 21221800601 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221800601) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78599127 + ... + 78599396.

It is an arithmetic number, because the mean of its divisors is an integer number (2357977860).

Almost surely, 2^21221800605 is an apocalyptic number.

It is an amenable number.

21221800605 is a deficient number, since it is larger than the sum of its proper divisors (16505845155).

21221800605 is a wasteful number, since it uses less digits than its factorization.

21221800605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157198537 (or 157198531 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The spelling of 21221800605 in words is "twenty-one billion, two hundred twenty-one million, eight hundred thousand, six hundred five".