21000101 has 4 divisors (see below), whose sum is σ = 21117600. Its totient is φ = 20882604.

The previous prime is 21000097. The next prime is 21000103. The reversal of 21000101 is 10100012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21000101 - 2² = 21000097 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000103) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 58481 + ... + 58838.

It is an arithmetic number, because the mean of its divisors is an integer number (5279400).

Almost surely, 2^21000101 is an apocalyptic number.

It is an amenable number.

21000101 is a deficient number, since it is larger than the sum of its proper divisors (117499).

21000101 is a wasteful number, since it uses less digits than its factorization.

21000101 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117498.

The product of its (nonzero) digits is 2, while the sum is 5.

The square root of 21000101 is about 4582.5867149460. The cubic root of 21000101 is about 275.8928599411.

Adding to 21000101 its reverse (10100012), we get a palindrome (31100113).

Multiplying 21000101 by its reverse (10100012), we get a palindrome (212101272101212).

The spelling of 21000101 in words is "twenty-one million, one hundred one", and thus it is an aban number.