21878575 has 12 divisors (see below), whose sum is σ = 28725840. Its totient is φ = 16472960.

The previous prime is 21878573. The next prime is 21878621. The reversal of 21878575 is 57587812.

It is not a de Polignac number, because 21878575 - 2¹ = 21878573 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878573) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25315 + ... + 26164.

It is an arithmetic number, because the mean of its divisors is an integer number (2393820).

Almost surely, 2^21878575 is an apocalyptic number.

21878575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21878575 is a deficient number, since it is larger than the sum of its proper divisors (6847265).

21878575 is a wasteful number, since it uses less digits than its factorization.

21878575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51506 (or 51501 counting only the distinct ones).

The product of its digits is 156800, while the sum is 43.

The square root of 21878575 is about 4677.4539014297. The cubic root of 21878575 is about 279.6874701684.

The spelling of 21878575 in words is "twenty-one million, eight hundred seventy-eight thousand, five hundred seventy-five".