21158545 has 16 divisors (see below), whose sum is σ = 26404560. Its totient is φ = 16257024.

The previous prime is 21158519. The next prime is 21158549. The reversal of 21158545 is 54585112.

It can be written as a sum of positive squares in 8 ways, for example, as 3214849 + 17943696 = 1793^2 + 4236^2 .

It is a cyclic number.

It is not a de Polignac number, because 21158545 - 2²³ = 12769937 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21158549) 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 15 ways as a sum of consecutive naturals, for example, 48649 + ... + 49081.

It is an arithmetic number, because the mean of its divisors is an integer number (1650285).

Almost surely, 2^21158545 is an apocalyptic number.

It is an amenable number.

21158545 is a deficient number, since it is larger than the sum of its proper divisors (5246015).

21158545 is a wasteful number, since it uses less digits than its factorization.

21158545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804.

The product of its digits is 8000, while the sum is 31.

The square root of 21158545 is about 4599.8418451073. The cubic root of 21158545 is about 276.5849849998.

The spelling of 21158545 in words is "twenty-one million, one hundred fifty-eight thousand, five hundred forty-five".