21506043 has 16 divisors (see below), whose sum is σ = 32506880. Its totient is φ = 12537504.

The previous prime is 21506041. The next prime is 21506059. The reversal of 21506043 is 34060512.

It is a happy number.

It is not a de Polignac number, because 21506043 - 2¹ = 21506041 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21506041) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13771 + ... + 15252.

It is an arithmetic number, because the mean of its divisors is an integer number (2031680).

Almost surely, 2^21506043 is an apocalyptic number.

21506043 is a deficient number, since it is larger than the sum of its proper divisors (11000837).

21506043 is a wasteful number, since it uses less digits than its factorization.

21506043 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29058.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21506043 is about 4637.4608354141. The cubic root of 21506043 is about 278.0909377635.

Adding to 21506043 its reverse (34060512), we get a palindrome (55566555).

The spelling of 21506043 in words is "twenty-one million, five hundred six thousand, forty-three".