21354437 has 4 divisors (see below), whose sum is σ = 22997100. Its totient is φ = 19711776.

The previous prime is 21354433. The next prime is 21354449. The reversal of 21354437 is 73445312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4330561 + 17023876 = 2081^2 + 4126^2 .

It is a cyclic number.

It is not a de Polignac number, because 21354437 - 2² = 21354433 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 (21354433) 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, 821312 + ... + 821337.

It is an arithmetic number, because the mean of its divisors is an integer number (5749275).

Almost surely, 2^21354437 is an apocalyptic number.

It is an amenable number.

21354437 is a deficient number, since it is larger than the sum of its proper divisors (1642663).

21354437 is a wasteful number, since it uses less digits than its factorization.

21354437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1642662.

The product of its digits is 10080, while the sum is 29.

The square root of 21354437 is about 4621.0861277410. The cubic root of 21354437 is about 277.4359325083.

Adding to 21354437 its reverse (73445312), we get a palindrome (94799749).

The spelling of 21354437 in words is "twenty-one million, three hundred fifty-four thousand, four hundred thirty-seven".