21555189 has 6 divisors (see below), whose sum is σ = 31135286. Its totient is φ = 14370120.

The previous prime is 21555181. The next prime is 21555197. The reversal of 21555189 is 98155512.

It is a happy number.

21555189 is a `hidden beast` number, since 21 + 5 + 551 + 89 = 666.

It is an interprime number because it is at equal distance from previous prime (21555181) and next prime (21555197).

It can be written as a sum of positive squares in only one way, i.e., 20520900 + 1034289 = 4530^2 + 1017^2 .

It is not a de Polignac number, because 21555189 - 2³ = 21555181 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555181) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1197502 + ... + 1197519.

Almost surely, 2^21555189 is an apocalyptic number.

It is an amenable number.

21555189 is a deficient number, since it is larger than the sum of its proper divisors (9580097).

21555189 is a wasteful number, since it uses less digits than its factorization.

21555189 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2395027 (or 2395024 counting only the distinct ones).

The product of its digits is 18000, while the sum is 36.

The square root of 21555189 is about 4642.7566164941. The cubic root of 21555189 is about 278.3026094269.

The spelling of 21555189 in words is "twenty-one million, five hundred fifty-five thousand, one hundred eighty-nine".