21918499 has 4 divisors (see below), whose sum is σ = 21957064. Its totient is φ = 21879936.

The previous prime is 21918473. The next prime is 21918509. The reversal of 21918499 is 99481912.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21918499 - 2¹³ = 21910307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21913499) 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 3 ways as a sum of consecutive naturals, for example, 18417 + ... + 19570.

It is an arithmetic number, because the mean of its divisors is an integer number (5489266).

Almost surely, 2^21918499 is an apocalyptic number.

21918499 is a deficient number, since it is larger than the sum of its proper divisors (38565).

21918499 is an equidigital number, since it uses as much as digits as its factorization.

21918499 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38564.

The product of its digits is 46656, while the sum is 43.

The square root of 21918499 is about 4681.7196626881. The cubic root of 21918499 is about 279.8574912566.

It can be divided in two parts, 219 and 18499, that multiplied together give a triangular number (4051281 = T₂₈₄₆).

The spelling of 21918499 in words is "twenty-one million, nine hundred eighteen thousand, four hundred ninety-nine".