21678349 has 16 divisors (see below), whose sum is σ = 28619136. Its totient is φ = 15897600.

The previous prime is 21678347. The next prime is 21678361. The reversal of 21678349 is 94387612.

It is a cyclic number.

It is not a de Polignac number, because 21678349 - 2¹ = 21678347 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21678343) 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 in 15 ways as a sum of consecutive naturals, for example, 6972 + ... + 9589.

It is an arithmetic number, because the mean of its divisors is an integer number (1788696).

Almost surely, 2^21678349 is an apocalyptic number.

It is an amenable number.

21678349 is a deficient number, since it is larger than the sum of its proper divisors (6940787).

21678349 is a wasteful number, since it uses less digits than its factorization.

21678349 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16596.

The product of its digits is 72576, while the sum is 40.

The square root of 21678349 is about 4656.0013960479. The cubic root of 21678349 is about 278.8316494847.

The spelling of 21678349 in words is "twenty-one million, six hundred seventy-eight thousand, three hundred forty-nine".