21788955 has 24 divisors (see below), whose sum is σ = 37887408. Its totient is φ = 11583936.

The previous prime is 21788933. The next prime is 21788959. The reversal of 21788955 is 55988712.

It is a happy number.

It is not a de Polignac number, because 21788955 - 2⁷ = 21788827 is a prime.

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

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 21788955.

It is not an unprimeable number, because it can be changed into a prime (21788959) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19389 + ... + 20481.

It is an arithmetic number, because the mean of its divisors is an integer number (1578642).

Almost surely, 2^21788955 is an apocalyptic number.

21788955 is a deficient number, since it is larger than the sum of its proper divisors (16098453).

21788955 is a wasteful number, since it uses less digits than its factorization.

21788955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1547 (or 1544 counting only the distinct ones).

The product of its digits is 201600, while the sum is 45.

The square root of 21788955 is about 4667.8640725711. The cubic root of 21788955 is about 279.3050580886.

The spelling of 21788955 in words is "twenty-one million, seven hundred eighty-eight thousand, nine hundred fifty-five".