21021678 has 24 divisors (see below), whose sum is σ = 47528208. Its totient is φ = 6702432.

The previous prime is 21021667. The next prime is 21021683. The reversal of 21021678 is 87612012.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 24975 + ... + 25802.

It is an arithmetic number, because the mean of its divisors is an integer number (1980342).

Almost surely, 2^21021678 is an apocalyptic number.

21021678 is an abundant number, since it is smaller than the sum of its proper divisors (26506530).

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

21021678 is a wasteful number, since it uses less digits than its factorization.

21021678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50808 (or 50805 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21021678 is about 4584.9403485760. The cubic root of 21021678 is about 275.9873182579.

The spelling of 21021678 in words is "twenty-one million, twenty-one thousand, six hundred seventy-eight".