21402978 has 8 divisors (see below), whose sum is σ = 42805968. Its totient is φ = 7134324.

The previous prime is 21402977. The next prime is 21403013. The reversal of 21402978 is 87920412.

It is a happy number.

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

21402978 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21402971) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 1783576 + ... + 1783587.

It is an arithmetic number, because the mean of its divisors is an integer number (5350746).

Almost surely, 2^21402978 is an apocalyptic number.

21402978 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21402978 is a wasteful number, since it uses less digits than its factorization.

21402978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3567168.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21402978 is about 4626.3352667095. The cubic root of 21402978 is about 277.6459876280.

The spelling of 21402978 in words is "twenty-one million, four hundred two thousand, nine hundred seventy-eight".