21872237 has 2 divisors, whose sum is σ = 21872238. Its totient is φ = 21872236.

The previous prime is 21872231. The next prime is 21872269. The reversal of 21872237 is 73227812.

It is an a-pointer prime, because the next prime (21872269) can be obtained adding 21872237 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21659716 + 212521 = 4654^2 + 461^2 .

It is a cyclic number.

It is not a de Polignac number, because 21872237 - 2¹² = 21868141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21872231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936118 + 10936119.

It is an arithmetic number, because the mean of its divisors is an integer number (10936119).

Almost surely, 2^21872237 is an apocalyptic number.

It is an amenable number.

21872237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872237 is an equidigital number, since it uses as much as digits as its factorization.

21872237 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 32.

The square root of 21872237 is about 4676.7763470151. The cubic root of 21872237 is about 279.6604600244.

The spelling of 21872237 in words is "twenty-one million, eight hundred seventy-two thousand, two hundred thirty-seven".