21506629 has 2 divisors, whose sum is σ = 21506630. Its totient is φ = 21506628.

The previous prime is 21506627. The next prime is 21506647. The reversal of 21506629 is 92660512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16564900 + 4941729 = 4070^2 + 2223^2 .

It is a cyclic number.

It is not a de Polignac number, because 21506629 - 2¹ = 21506627 is a prime.

Together with 21506627, 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 21506629.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21506627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10753314 + 10753315.

It is an arithmetic number, because the mean of its divisors is an integer number (10753315).

Almost surely, 2^21506629 is an apocalyptic number.

It is an amenable number.

21506629 is a deficient number, since it is larger than the sum of its proper divisors (1).

21506629 is an equidigital number, since it uses as much as digits as its factorization.

21506629 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 21506629 is about 4637.5240161103. The cubic root of 21506629 is about 278.0934635622.

The spelling of 21506629 in words is "twenty-one million, five hundred six thousand, six hundred twenty-nine".