21907429 has 2 divisors, whose sum is σ = 21907430. Its totient is φ = 21907428.

The previous prime is 21907397. The next prime is 21907433. The reversal of 21907429 is 92470912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12285025 + 9622404 = 3505^2 + 3102^2 .

It is a cyclic number.

It is not a de Polignac number, because 21907429 - 2⁵ = 21907397 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21907394 and 21907403.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21907469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953714 + 10953715.

It is an arithmetic number, because the mean of its divisors is an integer number (10953715).

Almost surely, 2^21907429 is an apocalyptic number.

It is an amenable number.

21907429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21907429 is an equidigital number, since it uses as much as digits as its factorization.

21907429 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 21907429 is about 4680.5372554868. The cubic root of 21907429 is about 279.8103690498.

The spelling of 21907429 in words is "twenty-one million, nine hundred seven thousand, four hundred twenty-nine".