21386971 has 2 divisors, whose sum is σ = 21386972. Its totient is φ = 21386970.

The previous prime is 21386947. The next prime is 21387001. The reversal of 21386971 is 17968312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21386971 - 2¹⁹ = 20862683 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 21386971.

It is not a weakly prime, because it can be changed into another prime (21386921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693485 + 10693486.

It is an arithmetic number, because the mean of its divisors is an integer number (10693486).

Almost surely, 2^21386971 is an apocalyptic number.

21386971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21386971 is an equidigital number, since it uses as much as digits as its factorization.

21386971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 37.

The square root of 21386971 is about 4624.6049561017. The cubic root of 21386971 is about 277.5767544629.

The spelling of 21386971 in words is "twenty-one million, three hundred eighty-six thousand, nine hundred seventy-one".