21818437 has 8 divisors (see below), whose sum is σ = 22420440. Its totient is φ = 21219840.

The previous prime is 21818431. The next prime is 21818449. The reversal of 21818437 is 73481812.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1079521 + 20738916 = 1039^2 + 4554^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21818437 - 2⁷ = 21818309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21818431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17139 + ... + 18367.

It is an arithmetic number, because the mean of its divisors is an integer number (2802555).

Almost surely, 2^21818437 is an apocalyptic number.

It is an amenable number.

21818437 is a deficient number, since it is larger than the sum of its proper divisors (602003).

21818437 is a wasteful number, since it uses less digits than its factorization.

21818437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1703.

The product of its digits is 10752, while the sum is 34.

The square root of 21818437 is about 4671.0209804710. The cubic root of 21818437 is about 279.4309744924.

The spelling of 21818437 in words is "twenty-one million, eight hundred eighteen thousand, four hundred thirty-seven".