21018929 has 2 divisors, whose sum is σ = 21018930. Its totient is φ = 21018928.

The previous prime is 21018869. The next prime is 21018931. The reversal of 21018929 is 92981012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 3713329 = 4160^2 + 1927^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21018929 is a prime.

Together with 21018931, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21018895 and 21018904.

It is not a weakly prime, because it can be changed into another prime (21018979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10509464 + 10509465.

It is an arithmetic number, because the mean of its divisors is an integer number (10509465).

Almost surely, 2^21018929 is an apocalyptic number.

It is an amenable number.

21018929 is a deficient number, since it is larger than the sum of its proper divisors (1).

21018929 is an equidigital number, since it uses as much as digits as its factorization.

21018929 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 21018929 is about 4584.6405529769. The cubic root of 21018929 is about 275.9752874674.

The spelling of 21018929 in words is "twenty-one million, eighteen thousand, nine hundred twenty-nine".