21801851 has 2 divisors, whose sum is σ = 21801852. Its totient is φ = 21801850.

The previous prime is 21801841. The next prime is 21801869. The reversal of 21801851 is 15810812.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21801851 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21801851.

It is not a weakly prime, because it can be changed into another prime (21801811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900925 + 10900926.

It is an arithmetic number, because the mean of its divisors is an integer number (10900926).

Almost surely, 2^21801851 is an apocalyptic number.

21801851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801851 is an equidigital number, since it uses as much as digits as its factorization.

21801851 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 21801851 is about 4669.2452280856. The cubic root of 21801851 is about 279.3601503384.

The spelling of 21801851 in words is "twenty-one million, eight hundred one thousand, eight hundred fifty-one".