21578971 has 2 divisors, whose sum is σ = 21578972. Its totient is φ = 21578970.

The previous prime is 21578941. The next prime is 21578981. The reversal of 21578971 is 17987512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21578971 - 2¹¹ = 21576923 is a prime.

It is not a weakly prime, because it can be changed into another prime (21578941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10789485 + 10789486.

It is an arithmetic number, because the mean of its divisors is an integer number (10789486).

Almost surely, 2^21578971 is an apocalyptic number.

21578971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21578971 is an equidigital number, since it uses as much as digits as its factorization.

21578971 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35280, while the sum is 40.

The square root of 21578971 is about 4645.3171043536. The cubic root of 21578971 is about 278.4049229199.

The spelling of 21578971 in words is "twenty-one million, five hundred seventy-eight thousand, nine hundred seventy-one".