21372187 has 2 divisors, whose sum is σ = 21372188. Its totient is φ = 21372186.

The previous prime is 21372181. The next prime is 21372227. The reversal of 21372187 is 78127312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21372187 - 2⁷ = 21372059 is a prime.

It is not a weakly prime, because it can be changed into another prime (21372181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10686093 + 10686094.

It is an arithmetic number, because the mean of its divisors is an integer number (10686094).

Almost surely, 2^21372187 is an apocalyptic number.

21372187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21372187 is an equidigital number, since it uses as much as digits as its factorization.

21372187 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4704, while the sum is 31.

The square root of 21372187 is about 4623.0062729787. The cubic root of 21372187 is about 277.5127803004.

Adding to 21372187 its reverse (78127312), we get a palindrome (99499499).

The spelling of 21372187 in words is "twenty-one million, three hundred seventy-two thousand, one hundred eighty-seven".