21648931 has 2 divisors, whose sum is σ = 21648932. Its totient is φ = 21648930.

The previous prime is 21648901. The next prime is 21648937. The reversal of 21648931 is 13984612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21648931 - 2¹⁹ = 21124643 is a prime.

It is a super-2 number, since 2×21648931² = 937352426885522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21648937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10824465 + 10824466.

It is an arithmetic number, because the mean of its divisors is an integer number (10824466).

Almost surely, 2^21648931 is an apocalyptic number.

21648931 is a deficient number, since it is larger than the sum of its proper divisors (1).

21648931 is an equidigital number, since it uses as much as digits as its factorization.

21648931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 34.

The square root of 21648931 is about 4652.8411750241. The cubic root of 21648931 is about 278.7054654801.

The spelling of 21648931 in words is "twenty-one million, six hundred forty-eight thousand, nine hundred thirty-one".