21155329 has 4 divisors (see below), whose sum is σ = 22782676. Its totient is φ = 19527984.

The previous prime is 21155287. The next prime is 21155339. The reversal of 21155329 is 92355112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4631104 + 16524225 = 2152^2 + 4065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21155329 - 2⁷ = 21155201 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21155297 and 21155306.

It is not an unprimeable number, because it can be changed into a prime (21155339) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 813654 + ... + 813679.

It is an arithmetic number, because the mean of its divisors is an integer number (5695669).

Almost surely, 2^21155329 is an apocalyptic number.

It is an amenable number.

21155329 is a deficient number, since it is larger than the sum of its proper divisors (1627347).

21155329 is a wasteful number, since it uses less digits than its factorization.

21155329 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1627346.

The product of its digits is 2700, while the sum is 28.

The square root of 21155329 is about 4599.4922545864. The cubic root of 21155329 is about 276.5709710812.

The spelling of 21155329 in words is "twenty-one million, one hundred fifty-five thousand, three hundred twenty-nine".