21137817 has 8 divisors (see below), whose sum is σ = 29841696. Its totient is φ = 13262912.

The previous prime is 21137813. The next prime is 21137819. The reversal of 21137817 is 71873112.

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 21137817 - 2² = 21137813 is a prime.

It is a super-3 number, since 3×21137817³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21137813) 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, 207183 + ... + 207284.

It is an arithmetic number, because the mean of its divisors is an integer number (3730212).

Almost surely, 2^21137817 is an apocalyptic number.

It is an amenable number.

21137817 is a deficient number, since it is larger than the sum of its proper divisors (8703879).

21137817 is a wasteful number, since it uses less digits than its factorization.

21137817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 414487.

The product of its digits is 2352, while the sum is 30.

The square root of 21137817 is about 4597.5881720746. The cubic root of 21137817 is about 276.4946365265.

The spelling of 21137817 in words is "twenty-one million, one hundred thirty-seven thousand, eight hundred seventeen".