21608437 has 2 divisors, whose sum is σ = 21608438. Its totient is φ = 21608436.

The previous prime is 21608429. The next prime is 21608443. The reversal of 21608437 is 73480612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11930116 + 9678321 = 3454^2 + 3111^2 .

It is a cyclic number.

It is not a de Polignac number, because 21608437 - 2³ = 21608429 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21608399 and 21608408.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21608417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804218 + 10804219.

It is an arithmetic number, because the mean of its divisors is an integer number (10804219).

Almost surely, 2^21608437 is an apocalyptic number.

It is an amenable number.

21608437 is a deficient number, since it is larger than the sum of its proper divisors (1).

21608437 is an equidigital number, since it uses as much as digits as its factorization.

21608437 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 31.

The square root of 21608437 is about 4648.4876035115. The cubic root of 21608437 is about 278.5315855606.

The spelling of 21608437 in words is "twenty-one million, six hundred eight thousand, four hundred thirty-seven".