211220021 has 16 divisors (see below), whose sum is σ = 224294400. Its totient is φ = 198578688.

The previous prime is 211220011. The next prime is 211220027. The reversal of 211220021 is 120022112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 211220021 - 2¹⁴ = 211203637 is a prime.

It is a super-2 number, since 2×211220021² = 89227794542480882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 211219984 and 211220011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211220027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 480920 + ... + 481358.

It is an arithmetic number, because the mean of its divisors is an integer number (14018400).

Almost surely, 2^211220021 is an apocalyptic number.

It is an amenable number.

211220021 is a deficient number, since it is larger than the sum of its proper divisors (13074379).

211220021 is a wasteful number, since it uses less digits than its factorization.

211220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 868.

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

The square root of 211220021 is about 14533.4105082049. The cubic root of 211220021 is about 595.5410383748.

Adding to 211220021 its reverse (120022112), we get a palindrome (331242133).

The spelling of 211220021 in words is "two hundred eleven million, two hundred twenty thousand, twenty-one".