21437818 has 4 divisors (see below), whose sum is σ = 32156730. Its totient is φ = 10718908.

The previous prime is 21437813. The next prime is 21437839. The reversal of 21437818 is 81873412.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 13126129 + 8311689 = 3623^2 + 2883^2 .

It is a super-2 number, since 2×21437818² = 919160081202248, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21437813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5359453 + ... + 5359456.

Almost surely, 2^21437818 is an apocalyptic number.

21437818 is a deficient number, since it is larger than the sum of its proper divisors (10718912).

21437818 is a wasteful number, since it uses less digits than its factorization.

21437818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10718911.

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

The square root of 21437818 is about 4630.0991350078. The cubic root of 21437818 is about 277.7965576755.

The spelling of 21437818 in words is "twenty-one million, four hundred thirty-seven thousand, eight hundred eighteen".