21155929 has 4 divisors (see below), whose sum is σ = 22075776. Its totient is φ = 20236084.

The previous prime is 21155921. The next prime is 21155977. The reversal of 21155929 is 92955112.

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 21155929 - 2³ = 21155921 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21155894 and 21155903.

It is not an unprimeable number, because it can be changed into a prime (21155921) 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, 459889 + ... + 459934.

It is an arithmetic number, because the mean of its divisors is an integer number (5518944).

Almost surely, 2^21155929 is an apocalyptic number.

It is an amenable number.

21155929 is a deficient number, since it is larger than the sum of its proper divisors (919847).

21155929 is an equidigital number, since it uses as much as digits as its factorization.

21155929 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 919846.

The product of its digits is 8100, while the sum is 34.

The square root of 21155929 is about 4599.5574787147. The cubic root of 21155929 is about 276.5735857261.

The spelling of 21155929 in words is "twenty-one million, one hundred fifty-five thousand, nine hundred twenty-nine".