21155829 has 4 divisors (see below), whose sum is σ = 28207776. Its totient is φ = 14103884.

The previous prime is 21155789. The next prime is 21155839. The reversal of 21155829 is 92855112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21155829 - 2¹² = 21151733 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21155829.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155839) 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, 3525969 + ... + 3525974.

It is an arithmetic number, because the mean of its divisors is an integer number (7051944).

Almost surely, 2^21155829 is an apocalyptic number.

It is an amenable number.

21155829 is a deficient number, since it is larger than the sum of its proper divisors (7051947).

21155829 is an equidigital number, since it uses as much as digits as its factorization.

21155829 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7051946.

The product of its digits is 7200, while the sum is 33.

The square root of 21155829 is about 4599.5466080908. The cubic root of 21155829 is about 276.5731499554.

The spelling of 21155829 in words is "twenty-one million, one hundred fifty-five thousand, eight hundred twenty-nine".