21739829 has 2 divisors, whose sum is σ = 21739830. Its totient is φ = 21739828.

The previous prime is 21739801. The next prime is 21739849. The reversal of 21739829 is 92893712.

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., 20295025 + 1444804 = 4505^2 + 1202^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21739829 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21739849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10869914 + 10869915.

It is an arithmetic number, because the mean of its divisors is an integer number (10869915).

Almost surely, 2^21739829 is an apocalyptic number.

It is an amenable number.

21739829 is a deficient number, since it is larger than the sum of its proper divisors (1).

21739829 is an equidigital number, since it uses as much as digits as its factorization.

21739829 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 41.

The square root of 21739829 is about 4662.5989533735. The cubic root of 21739829 is about 279.0949904153.

The spelling of 21739829 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred twenty-nine".