21211001001 has 6 divisors (see below), whose sum is σ = 30638112570. Its totient is φ = 14140667328.

The previous prime is 21211000973. The next prime is 21211001027. The reversal of 21211001001 is 10010011212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21111799401 + 99201600 = 145299^2 + 9960^2 .

It is not a de Polignac number, because 21211001001 - 2¹³ = 21210992809 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2356777889 = 21211001001 / (2 + 1 + 2 + 1 + 1 + 0 + 0 + 1 + 0 + 0 + 1).

It is not an unprimeable number, because it can be changed into a prime (21211001081) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1178388936 + ... + 1178388953.

It is an arithmetic number, because the mean of its divisors is an integer number (5106352095).

Almost surely, 2^21211001001 is an apocalyptic number.

It is an amenable number.

21211001001 is a deficient number, since it is larger than the sum of its proper divisors (9427111569).

21211001001 is a wasteful number, since it uses less digits than its factorization.

21211001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2356777895 (or 2356777892 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21211001001 its reverse (10010011212), we get a palindrome (31221012213).

The spelling of 21211001001 in words is "twenty-one billion, two hundred eleven million, one thousand, one".