21339978 has 16 divisors (see below), whose sum is σ = 46560096. Its totient is φ = 6466640.

The previous prime is 21339977. The next prime is 21339979. The reversal of 21339978 is 87993312.

It is an interprime number because it is at equal distance from previous prime (21339977) and next prime (21339979).

It is a super-2 number, since 2×21339978² = 910789322080968, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21339971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161601 + ... + 161732.

It is an arithmetic number, because the mean of its divisors is an integer number (2910006).

Almost surely, 2^21339978 is an apocalyptic number.

21339978 is an abundant number, since it is smaller than the sum of its proper divisors (25220118).

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

21339978 is a wasteful number, since it uses less digits than its factorization.

21339978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323349.

The product of its digits is 81648, while the sum is 42.

The square root of 21339978 is about 4619.5214037820. The cubic root of 21339978 is about 277.3733014671.

The spelling of 21339978 in words is "twenty-one million, three hundred thirty-nine thousand, nine hundred seventy-eight".