21058978 has 8 divisors (see below), whose sum is σ = 31608000. Its totient is φ = 10522980.

The previous prime is 21058963. The next prime is 21058979. The reversal of 21058978 is 87985012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21058978.

It is not an unprimeable number, because it can be changed into a prime (21058979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4243 + ... + 7753.

It is an arithmetic number, because the mean of its divisors is an integer number (3951000).

Almost surely, 2^21058978 is an apocalyptic number.

21058978 is a deficient number, since it is larger than the sum of its proper divisors (10549022).

21058978 is a wasteful number, since it uses less digits than its factorization.

21058978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6512.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 21058978 is about 4589.0062104992. The cubic root of 21058978 is about 276.1504553198.

The spelling of 21058978 in words is "twenty-one million, fifty-eight thousand, nine hundred seventy-eight".