21646351 has 2 divisors, whose sum is σ = 21646352. Its totient is φ = 21646350.

The previous prime is 21646349. The next prime is 21646363. The reversal of 21646351 is 15364612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21646351 - 2¹ = 21646349 is a prime.

Together with 21646349, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21643351) 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, 10823175 + 10823176.

It is an arithmetic number, because the mean of its divisors is an integer number (10823176).

Almost surely, 2^21646351 is an apocalyptic number.

21646351 is a deficient number, since it is larger than the sum of its proper divisors (1).

21646351 is an equidigital number, since it uses as much as digits as its factorization.

21646351 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 28.

The square root of 21646351 is about 4652.5639168097. The cubic root of 21646351 is about 278.6943935144.

It can be divided in two parts, 2164 and 6351, that added together give a triangular number (8515 = T₁₃₀).

The spelling of 21646351 in words is "twenty-one million, six hundred forty-six thousand, three hundred fifty-one".