21167978 has 16 divisors (see below), whose sum is σ = 35298816. Its totient is φ = 9454320.

The previous prime is 21167969. The next prime is 21167987. The reversal of 21167978 is 87976112.

It is an interprime number because it is at equal distance from previous prime (21167969) and next prime (21167987).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12326 + ... + 13937.

It is an arithmetic number, because the mean of its divisors is an integer number (2206176).

Almost surely, 2^21167978 is an apocalyptic number.

21167978 is a deficient number, since it is larger than the sum of its proper divisors (14130838).

21167978 is a wasteful number, since it uses less digits than its factorization.

21167978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26309.

The product of its digits is 42336, while the sum is 41.

The square root of 21167978 is about 4600.8670921903. The cubic root of 21167978 is about 276.6260816905.

The spelling of 21167978 in words is "twenty-one million, one hundred sixty-seven thousand, nine hundred seventy-eight".