21871905 has 32 divisors (see below), whose sum is σ = 38734848. Its totient is φ = 10449600.

The previous prime is 21871903. The next prime is 21871931. The reversal of 21871905 is 50917812.

It is not a de Polignac number, because 21871905 - 2¹ = 21871903 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21871903) 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 31 ways as a sum of consecutive naturals, for example, 10782 + ... + 12648.

It is an arithmetic number, because the mean of its divisors is an integer number (1210464).

Almost surely, 2^21871905 is an apocalyptic number.

It is an amenable number.

21871905 is a deficient number, since it is larger than the sum of its proper divisors (16862943).

21871905 is a wasteful number, since it uses less digits than its factorization.

21871905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1957.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21871905 is about 4676.7408523458. The cubic root of 21871905 is about 279.6590450229.

The spelling of 21871905 in words is "twenty-one million, eight hundred seventy-one thousand, nine hundred five".