21608831 has 2 divisors, whose sum is σ = 21608832. Its totient is φ = 21608830.

The previous prime is 21608827. The next prime is 21608837. The reversal of 21608831 is 13880612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21608831 - 2² = 21608827 is a prime.

It is a super-2 number, since 2×21608831² = 933883154373122, which contains 22 as substring.

It is a plaindrome in base 8.

It is a junction number, because it is equal to n+sod(n) for n = 21608794 and 21608803.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21608837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804415 + 10804416.

It is an arithmetic number, because the mean of its divisors is an integer number (10804416).

Almost surely, 2^21608831 is an apocalyptic number.

21608831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21608831 is an equidigital number, since it uses as much as digits as its factorization.

21608831 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21608831 is about 4648.5299826935. The cubic root of 21608831 is about 278.5332784298.

The spelling of 21608831 in words is "twenty-one million, six hundred eight thousand, eight hundred thirty-one".