21428971 has 2 divisors, whose sum is σ = 21428972. Its totient is φ = 21428970.

The previous prime is 21428969. The next prime is 21428989. The reversal of 21428971 is 17982412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21428971 - 2¹ = 21428969 is a prime.

Together with 21428969, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21408971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10714485 + 10714486.

It is an arithmetic number, because the mean of its divisors is an integer number (10714486).

Almost surely, 2^21428971 is an apocalyptic number.

21428971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21428971 is an equidigital number, since it uses as much as digits as its factorization.

21428971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 34.

The square root of 21428971 is about 4629.1436573086. The cubic root of 21428971 is about 277.7583385448.

The spelling of 21428971 in words is "twenty-one million, four hundred twenty-eight thousand, nine hundred seventy-one".