21291029 has 2 divisors, whose sum is σ = 21291030. Its totient is φ = 21291028.

The previous prime is 21291019. The next prime is 21291091. The reversal of 21291029 is 92019212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20295025 + 996004 = 4505^2 + 998^2 .

It is a cyclic number.

It is not a de Polignac number, because 21291029 - 2¹² = 21286933 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21290989 and 21291007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21291019) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645514 + 10645515.

It is an arithmetic number, because the mean of its divisors is an integer number (10645515).

Almost surely, 2^21291029 is an apocalyptic number.

It is an amenable number.

21291029 is a deficient number, since it is larger than the sum of its proper divisors (1).

21291029 is an equidigital number, since it uses as much as digits as its factorization.

21291029 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21291029 is about 4614.2203024997. The cubic root of 21291029 is about 277.1610622616.

The spelling of 21291029 in words is "twenty-one million, two hundred ninety-one thousand, twenty-nine".