21971418 has 16 divisors (see below), whose sum is σ = 50220480. Its totient is φ = 6277536.

The previous prime is 21971413. The next prime is 21971437. The reversal of 21971418 is 81417912.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21971413) 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 7 ways as a sum of consecutive naturals, for example, 261523 + ... + 261606.

It is an arithmetic number, because the mean of its divisors is an integer number (3138780).

Almost surely, 2^21971418 is an apocalyptic number.

21971418 is an abundant number, since it is smaller than the sum of its proper divisors (28249062).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21971418 is a wasteful number, since it uses less digits than its factorization.

21971418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 523141.

The product of its digits is 4032, while the sum is 33.

The square root of 21971418 is about 4687.3679181391. The cubic root of 21971418 is about 280.0825351926.

The spelling of 21971418 in words is "twenty-one million, nine hundred seventy-one thousand, four hundred eighteen".