21158641 has 8 divisors (see below), whose sum is σ = 24675200. Its totient is φ = 18135684.

The previous prime is 21158633. The next prime is 21158671. The reversal of 21158641 is 14685112.

It is not a de Polignac number, because 21158641 - 2³ = 21158633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21158671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30501 + ... + 31186.

It is an arithmetic number, because the mean of its divisors is an integer number (3084400).

Almost surely, 2^21158641 is an apocalyptic number.

It is an amenable number.

21158641 is a deficient number, since it is larger than the sum of its proper divisors (3516559).

21158641 is an frugal number, since it uses more digits than its factorization.

21158641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61708 (or 61694 counting only the distinct ones).

The product of its digits is 1920, while the sum is 28.

The square root of 21158641 is about 4599.8522802368. The cubic root of 21158641 is about 276.5854033039.

The spelling of 21158641 in words is "twenty-one million, one hundred fifty-eight thousand, six hundred forty-one".