211428021 has 16 divisors (see below), whose sum is σ = 330035328. Its totient is φ = 117868800.

The previous prime is 211428017. The next prime is 211428059. The reversal of 211428021 is 120824112.

It is not a de Polignac number, because 211428021 - 2² = 211428017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211428011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 121920 + ... + 123641.

It is an arithmetic number, because the mean of its divisors is an integer number (20627208).

Almost surely, 2^211428021 is an apocalyptic number.

211428021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

211428021 is a deficient number, since it is larger than the sum of its proper divisors (118607307).

211428021 is a wasteful number, since it uses less digits than its factorization.

211428021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245612.

The product of its (nonzero) digits is 256, while the sum is 21.

The square root of 211428021 is about 14540.5646726666. The cubic root of 211428021 is about 595.7364616058.

It can be divided in two parts, 2114 and 28021, that added together give a triangular number (30135 = T₂₄₅).

The spelling of 211428021 in words is "two hundred eleven million, four hundred twenty-eight thousand, twenty-one".