21266018 has 4 divisors (see below), whose sum is σ = 31899030. Its totient is φ = 10633008.

The previous prime is 21266017. The next prime is 21266029. The reversal of 21266018 is 81066212.

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., 12581209 + 8684809 = 3547^2 + 2947^2 .

It is not an unprimeable number, because it can be changed into a prime (21266017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5316503 + ... + 5316506.

Almost surely, 2^21266018 is an apocalyptic number.

21266018 is a deficient number, since it is larger than the sum of its proper divisors (10633012).

21266018 is a wasteful number, since it uses less digits than its factorization.

21266018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10633011.

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 21266018 is about 4611.5092973993. The cubic root of 21266018 is about 277.0524908453.

The spelling of 21266018 in words is "twenty-one million, two hundred sixty-six thousand, eighteen".