21516829 has 2 divisors, whose sum is σ = 21516830. Its totient is φ = 21516828.

The previous prime is 21516827. The next prime is 21516853. The reversal of 21516829 is 92861512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13704804 + 7812025 = 3702^2 + 2795^2 .

It is a cyclic number.

It is not a de Polignac number, because 21516829 - 2¹ = 21516827 is a prime.

Together with 21516827, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21516794 and 21516803.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21516827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758414 + 10758415.

It is an arithmetic number, because the mean of its divisors is an integer number (10758415).

Almost surely, 2^21516829 is an apocalyptic number.

It is an amenable number.

21516829 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516829 is an equidigital number, since it uses as much as digits as its factorization.

21516829 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8640, while the sum is 34.

The square root of 21516829 is about 4638.6236105121. The cubic root of 21516829 is about 278.1374206295.

The spelling of 21516829 in words is "twenty-one million, five hundred sixteen thousand, eight hundred twenty-nine".