21523001 has 2 divisors, whose sum is σ = 21523002. Its totient is φ = 21523000.

The previous prime is 21522989. The next prime is 21523049. The reversal of 21523001 is 10032512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17007376 + 4515625 = 4124^2 + 2125^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21523001 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21522001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10761500 + 10761501.

It is an arithmetic number, because the mean of its divisors is an integer number (10761501).

Almost surely, 2^21523001 is an apocalyptic number.

It is an amenable number.

21523001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21523001 is an equidigital number, since it uses as much as digits as its factorization.

21523001 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21523001 is about 4639.2888463643. The cubic root of 21523001 is about 278.1640122189.

Adding to 21523001 its reverse (10032512), we get a palindrome (31555513).

The spelling of 21523001 in words is "twenty-one million, five hundred twenty-three thousand, one".