21571001 has 2 divisors, whose sum is σ = 21571002. Its totient is φ = 21571000.

The previous prime is 21570929. The next prime is 21571051. The reversal of 21571001 is 10017512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21114025 + 456976 = 4595^2 + 676^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21571001 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21571051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10785500 + 10785501.

It is an arithmetic number, because the mean of its divisors is an integer number (10785501).

Almost surely, 2^21571001 is an apocalyptic number.

It is an amenable number.

21571001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571001 is an equidigital number, since it uses as much as digits as its factorization.

21571001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 21571001 is about 4644.4591719596. The cubic root of 21571001 is about 278.3706432429.

Adding to 21571001 its reverse (10017512), we get a palindrome (31588513).

The spelling of 21571001 in words is "twenty-one million, five hundred seventy-one thousand, one".