21872857 has 4 divisors (see below), whose sum is σ = 23024080. Its totient is φ = 20721636.

The previous prime is 21872827. The next prime is 21872861. The reversal of 21872857 is 75827812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21872857 - 2¹¹ = 21870809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21872827) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 575583 + ... + 575620.

It is an arithmetic number, because the mean of its divisors is an integer number (5756020).

Almost surely, 2^21872857 is an apocalyptic number.

It is an amenable number.

21872857 is a deficient number, since it is larger than the sum of its proper divisors (1151223).

21872857 is a wasteful number, since it uses less digits than its factorization.

21872857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1151222.

The product of its digits is 62720, while the sum is 40.

The square root of 21872857 is about 4676.8426315197. The cubic root of 21872857 is about 279.6631024587.

The spelling of 21872857 in words is "twenty-one million, eight hundred seventy-two thousand, eight hundred fifty-seven".