21081678 has 24 divisors (see below), whose sum is σ = 44503848. Its totient is φ = 6656688.

The previous prime is 21081673. The next prime is 21081679. The reversal of 21081678 is 87618012.

It is a happy number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081673) 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, 2701 + ... + 7032.

It is an arithmetic number, because the mean of its divisors is an integer number (1854327).

Almost surely, 2^21081678 is an apocalyptic number.

21081678 is an abundant number, since it is smaller than the sum of its proper divisors (23422170).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21081678 is a wasteful number, since it uses less digits than its factorization.

21081678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9776 (or 9757 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 33.

The square root of 21081678 is about 4591.4788467334. The cubic root of 21081678 is about 276.2496428542.

The spelling of 21081678 in words is "twenty-one million, eighty-one thousand, six hundred seventy-eight".