21764218 has 16 divisors (see below), whose sum is σ = 37390464. Its totient is φ = 9307440.

The previous prime is 21764191. The next prime is 21764219. The reversal of 21764218 is 81246712.

It is a self number, because there is not a number n which added to its sum of digits gives 21764218.

It is not an unprimeable number, because it can be changed into a prime (21764219) 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 7 ways as a sum of consecutive naturals, for example, 6403 + ... + 9193.

It is an arithmetic number, because the mean of its divisors is an integer number (2336904).

Almost surely, 2^21764218 is an apocalyptic number.

21764218 is a deficient number, since it is larger than the sum of its proper divisors (15626246).

21764218 is a wasteful number, since it uses less digits than its factorization.

21764218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3357.

The product of its digits is 5376, while the sum is 31.

The square root of 21764218 is about 4665.2136071138. The cubic root of 21764218 is about 279.1993197220.

The spelling of 21764218 in words is "twenty-one million, seven hundred sixty-four thousand, two hundred eighteen".