21011001 has 8 divisors (see below), whose sum is σ = 30561504. Its totient is φ = 12733920.

The previous prime is 21010987. The next prime is 21011009. The reversal of 21011001 is 10011012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21011001 - 2⁹ = 21010489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21011009) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 318316 + ... + 318381.

It is an arithmetic number, because the mean of its divisors is an integer number (3820188).

Almost surely, 2^21011001 is an apocalyptic number.

It is an amenable number.

21011001 is a deficient number, since it is larger than the sum of its proper divisors (9550503).

21011001 is a wasteful number, since it uses less digits than its factorization.

21011001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636711.

The product of its (nonzero) digits is 2, while the sum is 6.

The square root of 21011001 is about 4583.7758453048. The cubic root of 21011001 is about 275.9405852993.

Adding to 21011001 its reverse (10011012), we get a palindrome (31022013).

Multiplying 21011001 by its reverse (10011012), we get a palindrome (210341383143012).

It can be divided in two parts, 210 and 11001, that added together give a palindrome (11211).

The spelling of 21011001 in words is "twenty-one million, eleven thousand, one".