21678291 has 12 divisors (see below), whose sum is σ = 31359120. Its totient is φ = 14430960.

The previous prime is 21678277. The next prime is 21678313. The reversal of 21678291 is 19287612.

It is not a de Polignac number, because 21678291 - 2⁹ = 21677779 is a prime.

It is a super-3 number, since 3×21678291³ (a number of 23 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21678211) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6961 + ... + 9581.

It is an arithmetic number, because the mean of its divisors is an integer number (2613260).

Almost surely, 2^21678291 is an apocalyptic number.

21678291 is a deficient number, since it is larger than the sum of its proper divisors (9680829).

21678291 is a wasteful number, since it uses less digits than its factorization.

21678291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3546 (or 3543 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21678291 is about 4655.9951675233. The cubic root of 21678291 is about 278.8314008149.

The spelling of 21678291 in words is "twenty-one million, six hundred seventy-eight thousand, two hundred ninety-one".