21221002001 has 2 divisors, whose sum is σ = 21221002002. Its totient is φ = 21221002000.

The previous prime is 21221001973. The next prime is 21221002027. The reversal of 21221002001 is 10020012212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19161203776 + 2059798225 = 138424^2 + 45385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221002001 - 2²² = 21216807697 is a prime.

It is not a weakly prime, because it can be changed into another prime (21221001001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610501000 + 10610501001.

It is an arithmetic number, because the mean of its divisors is an integer number (10610501001).

Almost surely, 2^21221002001 is an apocalyptic number.

It is an amenable number.

21221002001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221002001 is an equidigital number, since it uses as much as digits as its factorization.

21221002001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21221002001 its reverse (10020012212), we get a palindrome (31241014213).

The spelling of 21221002001 in words is "twenty-one billion, two hundred twenty-one million, two thousand, one".