21220101 has 12 divisors (see below), whose sum is σ = 35030112. Its totient is φ = 12125736.

The previous prime is 21220019. The next prime is 21220103. The reversal of 21220101 is 10102212.

It is not a de Polignac number, because 21220101 - 2⁹ = 21219589 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21220103) 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 in 11 ways as a sum of consecutive naturals, for example, 168351 + ... + 168476.

It is an arithmetic number, because the mean of its divisors is an integer number (2919176).

Almost surely, 2^21220101 is an apocalyptic number.

21220101 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21220101 is a deficient number, since it is larger than the sum of its proper divisors (13810011).

21220101 is a wasteful number, since it uses less digits than its factorization.

21220101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336840 (or 336837 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

The square root of 21220101 is about 4606.5280852286. The cubic root of 21220101 is about 276.8529457913.

Adding to 21220101 its reverse (10102212), we get a palindrome (31322313).

It can be divided in two parts, 21220 and 101, that added together give a triangular number (21321 = T₂₀₆).

The spelling of 21220101 in words is "twenty-one million, two hundred twenty thousand, one hundred one".