21082978 has 24 divisors (see below), whose sum is σ = 37118592. Its totient is φ = 8793912.

The previous prime is 21082961. The next prime is 21082981. The reversal of 21082978 is 87928012.

It is a super-2 number, since 2×21082978² = 888983922696968, which contains 22 as substring.

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 117693 + ... + 117871.

It is an arithmetic number, because the mean of its divisors is an integer number (1546608).

Almost surely, 2^21082978 is an apocalyptic number.

21082978 is a deficient number, since it is larger than the sum of its proper divisors (16035614).

21082978 is an equidigital number, since it uses as much as digits as its factorization.

21082978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414 (or 235 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 21082978 is about 4591.6204111403. The cubic root of 21082978 is about 276.2553210416.

The spelling of 21082978 in words is "twenty-one million, eighty-two thousand, nine hundred seventy-eight".