21487429 has 2 divisors, whose sum is σ = 21487430. Its totient is φ = 21487428.

The previous prime is 21487421. The next prime is 21487441. The reversal of 21487429 is 92478412.

21487429 is nontrivially palindromic in base 4.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17447329 + 4040100 = 4177^2 + 2010^2 .

It is a cyclic number.

It is not a de Polignac number, because 21487429 - 2³ = 21487421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21487421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10743714 + 10743715.

It is an arithmetic number, because the mean of its divisors is an integer number (10743715).

Almost surely, 2^21487429 is an apocalyptic number.

It is an amenable number.

21487429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21487429 is an equidigital number, since it uses as much as digits as its factorization.

21487429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 37.

The square root of 21487429 is about 4635.4534837489. The cubic root of 21487429 is about 278.0106831290.

The spelling of 21487429 in words is "twenty-one million, four hundred eighty-seven thousand, four hundred twenty-nine".