21878541 has 24 divisors (see below), whose sum is σ = 33718464. Its totient is φ = 13622400.

The previous prime is 21878531. The next prime is 21878567. The reversal of 21878541 is 14587812.

It is not a de Polignac number, because 21878541 - 2⁷ = 21878413 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21878496 and 21878505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878531) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 22630 + ... + 23576.

It is an arithmetic number, because the mean of its divisors is an integer number (1404936).

Almost surely, 2^21878541 is an apocalyptic number.

It is an amenable number.

21878541 is a deficient number, since it is larger than the sum of its proper divisors (11839923).

21878541 is a wasteful number, since it uses less digits than its factorization.

21878541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1121 (or 1118 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 21878541 is about 4677.4502669724. The cubic root of 21878541 is about 279.6873252873.

The spelling of 21878541 in words is "twenty-one million, eight hundred seventy-eight thousand, five hundred forty-one".