21975851 has 2 divisors, whose sum is σ = 21975852. Its totient is φ = 21975850.

The previous prime is 21975841. The next prime is 21975911. The reversal of 21975851 is 15857912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21975851 - 2¹⁸ = 21713707 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21975841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10987925 + 10987926.

It is an arithmetic number, because the mean of its divisors is an integer number (10987926).

Almost surely, 2^21975851 is an apocalyptic number.

21975851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21975851 is an equidigital number, since it uses as much as digits as its factorization.

21975851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25200, while the sum is 38.

The square root of 21975851 is about 4687.8407609474. The cubic root of 21975851 is about 280.1013706085.

The spelling of 21975851 in words is "twenty-one million, nine hundred seventy-five thousand, eight hundred fifty-one".