21678507 has 6 divisors (see below), whose sum is σ = 31313412. Its totient is φ = 14452332.

The previous prime is 21678491. The next prime is 21678509. The reversal of 21678507 is 70587612.

It is not a de Polignac number, because 21678507 - 2⁴ = 21678491 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (21678509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1204353 + ... + 1204370.

It is an arithmetic number, because the mean of its divisors is an integer number (5218902).

Almost surely, 2^21678507 is an apocalyptic number.

21678507 is a deficient number, since it is larger than the sum of its proper divisors (9634905).

21678507 is a wasteful number, since it uses less digits than its factorization.

21678507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2408729 (or 2408726 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 21678507 is about 4656.0183633658. The cubic root of 21678507 is about 278.8323268932.

The spelling of 21678507 in words is "twenty-one million, six hundred seventy-eight thousand, five hundred seven".