21872657 has 4 divisors (see below), whose sum is σ = 22243440. Its totient is φ = 21501876.

The previous prime is 21872647. The next prime is 21872663. The reversal of 21872657 is 75627812.

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 21872657 - 2⁶ = 21872593 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21872657.

It is not an unprimeable number, because it can be changed into a prime (21872647) 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, 185303 + ... + 185420.

It is an arithmetic number, because the mean of its divisors is an integer number (5560860).

Almost surely, 2^21872657 is an apocalyptic number.

It is an amenable number.

21872657 is a deficient number, since it is larger than the sum of its proper divisors (370783).

21872657 is an equidigital number, since it uses as much as digits as its factorization.

21872657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 370782.

The product of its digits is 47040, while the sum is 38.

The square root of 21872657 is about 4676.8212495241. The cubic root of 21872657 is about 279.6622500660.

The spelling of 21872657 in words is "twenty-one million, eight hundred seventy-two thousand, six hundred fifty-seven".