21921071 has 4 divisors (see below), whose sum is σ = 22677000. Its totient is φ = 21165144.

The previous prime is 21921059. The next prime is 21921083. The reversal of 21921071 is 17012912.

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

It is an interprime number because it is at equal distance from previous prime (21921059) and next prime (21921083).

It is a cyclic number.

It is not a de Polignac number, because 21921071 - 2¹⁰ = 21920047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21926071) 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, 377921 + ... + 377978.

It is an arithmetic number, because the mean of its divisors is an integer number (5669250).

Almost surely, 2^21921071 is an apocalyptic number.

21921071 is a deficient number, since it is larger than the sum of its proper divisors (755929).

21921071 is an equidigital number, since it uses as much as digits as its factorization.

21921071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 755928.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21921071 is about 4681.9943400222. The cubic root of 21921071 is about 279.8684373424.

Adding to 21921071 its reverse (17012912), we get a palindrome (38933983).

The spelling of 21921071 in words is "twenty-one million, nine hundred twenty-one thousand, seventy-one".