21318778 has 16 divisors (see below), whose sum is σ = 34524000. Its totient is φ = 9814896.

The previous prime is 21318767. The next prime is 21318821. The reversal of 21318778 is 87781312.

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, 13473 + ... + 14971.

It is an arithmetic number, because the mean of its divisors is an integer number (2157750).

Almost surely, 2^21318778 is an apocalyptic number.

21318778 is a deficient number, since it is larger than the sum of its proper divisors (13205222).

21318778 is a wasteful number, since it uses less digits than its factorization.

21318778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2061.

The product of its digits is 18816, while the sum is 37.

The square root of 21318778 is about 4617.2262236109. The cubic root of 21318778 is about 277.2814197368.

The spelling of 21318778 in words is "twenty-one million, three hundred eighteen thousand, seven hundred seventy-eight".