21003929 has 2 divisors, whose sum is σ = 21003930. Its totient is φ = 21003928.

The previous prime is 21003893. The next prime is 21003937. The reversal of 21003929 is 92930012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20043529 + 960400 = 4477^2 + 980^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003929 - 2⁸ = 21003673 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21003898 and 21003907.

It is not a weakly prime, because it can be changed into another prime (21003329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501964 + 10501965.

It is an arithmetic number, because the mean of its divisors is an integer number (10501965).

Almost surely, 2^21003929 is an apocalyptic number.

It is an amenable number.

21003929 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003929 is an equidigital number, since it uses as much as digits as its factorization.

21003929 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 21003929 is about 4583.0043639517. The cubic root of 21003929 is about 275.9096226177.

The spelling of 21003929 in words is "twenty-one million, three thousand, nine hundred twenty-nine".