21629009 has 2 divisors, whose sum is σ = 21629010. Its totient is φ = 21629008.

The previous prime is 21628969. The next prime is 21629021. The reversal of 21629009 is 90092612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10923025 + 10705984 = 3305^2 + 3272^2 .

It is a cyclic number.

It is not a de Polignac number, because 21629009 - 2⁸ = 21628753 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21629029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10814504 + 10814505.

It is an arithmetic number, because the mean of its divisors is an integer number (10814505).

Almost surely, 2^21629009 is an apocalyptic number.

It is an amenable number.

21629009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21629009 is an equidigital number, since it uses as much as digits as its factorization.

21629009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 21629009 is about 4650.6998398091. The cubic root of 21629009 is about 278.6199481812.

The spelling of 21629009 in words is "twenty-one million, six hundred twenty-nine thousand, nine".