21218901 has 8 divisors (see below), whose sum is σ = 30863904. Its totient is φ = 12859920.

The previous prime is 21218893. The next prime is 21218929. The reversal of 21218901 is 10981212.

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

It is not a de Polignac number, because 21218901 - 2³ = 21218893 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210901) 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, 321466 + ... + 321531.

It is an arithmetic number, because the mean of its divisors is an integer number (3857988).

Almost surely, 2^21218901 is an apocalyptic number.

It is an amenable number.

21218901 is a deficient number, since it is larger than the sum of its proper divisors (9645003).

21218901 is a wasteful number, since it uses less digits than its factorization.

21218901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 643011.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 21218901 is about 4606.3978334486. The cubic root of 21218901 is about 276.8477270006.

The spelling of 21218901 in words is "twenty-one million, two hundred eighteen thousand, nine hundred one".