21398137 has 4 divisors (see below), whose sum is σ = 21415680. Its totient is φ = 21380596.

The previous prime is 21398131. The next prime is 21398141. The reversal of 21398137 is 73189312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21398137 - 2¹⁹ = 20873849 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21398131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6793 + ... + 9430.

It is an arithmetic number, because the mean of its divisors is an integer number (5353920).

Almost surely, 2^21398137 is an apocalyptic number.

It is an amenable number.

21398137 is a deficient number, since it is larger than the sum of its proper divisors (17543).

21398137 is a wasteful number, since it uses less digits than its factorization.

21398137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17542.

The product of its digits is 9072, while the sum is 34.

The square root of 21398137 is about 4625.8120368212. The cubic root of 21398137 is about 277.6250530712.

The spelling of 21398137 in words is "twenty-one million, three hundred ninety-eight thousand, one hundred thirty-seven".