21020429 has 2 divisors, whose sum is σ = 21020430. Its totient is φ = 21020428.

The previous prime is 21020411. The next prime is 21020431. The reversal of 21020429 is 92402012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15721225 + 5299204 = 3965^2 + 2302^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020429 is a prime.

Together with 21020431, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020429.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510214 + 10510215.

It is an arithmetic number, because the mean of its divisors is an integer number (10510215).

Almost surely, 2^21020429 is an apocalyptic number.

It is an amenable number.

21020429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020429 is an equidigital number, since it uses as much as digits as its factorization.

21020429 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21020429 is about 4584.8041397643. The cubic root of 21020429 is about 275.9818522339.

The spelling of 21020429 in words is "twenty-one million, twenty thousand, four hundred twenty-nine".