21165437 has 4 divisors (see below), whose sum is σ = 21184800. Its totient is φ = 21146076.

The previous prime is 21165427. The next prime is 21165457. The reversal of 21165437 is 73456112.

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 21165437 - 2⁴ = 21165421 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 (21165427) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7937 + ... + 10262.

It is an arithmetic number, because the mean of its divisors is an integer number (5296200).

Almost surely, 2^21165437 is an apocalyptic number.

It is an amenable number.

21165437 is a deficient number, since it is larger than the sum of its proper divisors (19363).

21165437 is a wasteful number, since it uses less digits than its factorization.

21165437 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19362.

The product of its digits is 5040, while the sum is 29.

The square root of 21165437 is about 4600.5909403032. The cubic root of 21165437 is about 276.6150125337.

The spelling of 21165437 in words is "twenty-one million, one hundred sixty-five thousand, four hundred thirty-seven".