21018437 has 4 divisors (see below), whose sum is σ = 22929216. Its totient is φ = 19107660.

The previous prime is 21018407. The next prime is 21018461. The reversal of 21018437 is 73481012.

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 de Polignac number, because none of the positive numbers 2^k-21018437 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018407) 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, 955373 + ... + 955394.

It is an arithmetic number, because the mean of its divisors is an integer number (5732304).

Almost surely, 2^21018437 is an apocalyptic number.

It is an amenable number.

21018437 is a deficient number, since it is larger than the sum of its proper divisors (1910779).

21018437 is a wasteful number, since it uses less digits than its factorization.

21018437 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1910778.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21018437 is about 4584.5868952393. The cubic root of 21018437 is about 275.9731341559.

Adding to 21018437 its reverse (73481012), we get a palindrome (94499449).

The spelling of 21018437 in words is "twenty-one million, eighteen thousand, four hundred thirty-seven".