21815429 has 2 divisors, whose sum is σ = 21815430. Its totient is φ = 21815428.

The previous prime is 21815419. The next prime is 21815449. The reversal of 21815429 is 92451812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17447329 + 4368100 = 4177^2 + 2090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21815429 - 2²⁰ = 20766853 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21815395 and 21815404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21815419) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10907714 + 10907715.

It is an arithmetic number, because the mean of its divisors is an integer number (10907715).

Almost surely, 2^21815429 is an apocalyptic number.

It is an amenable number.

21815429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21815429 is an equidigital number, since it uses as much as digits as its factorization.

21815429 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 32.

The square root of 21815429 is about 4670.6989840922. The cubic root of 21815429 is about 279.4181326468.

The spelling of 21815429 in words is "twenty-one million, eight hundred fifteen thousand, four hundred twenty-nine".