21440971 has 4 divisors (see below), whose sum is σ = 21454272. Its totient is φ = 21427672.

The previous prime is 21440941. The next prime is 21440989. The reversal of 21440971 is 17904412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21440971 - 2⁷ = 21440843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21440941) 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 3 ways as a sum of consecutive naturals, for example, 3835 + ... + 7588.

It is an arithmetic number, because the mean of its divisors is an integer number (5363568).

Almost surely, 2^21440971 is an apocalyptic number.

21440971 is a deficient number, since it is larger than the sum of its proper divisors (13301).

21440971 is a wasteful number, since it uses less digits than its factorization.

21440971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13300.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21440971 is about 4630.4396119591. The cubic root of 21440971 is about 277.8101761263.

The spelling of 21440971 in words is "twenty-one million, four hundred forty thousand, nine hundred seventy-one".