212217921 has 8 divisors (see below), whose sum is σ = 314396960. Its totient is φ = 141478596.

The previous prime is 212217917. The next prime is 212217979. The reversal of 212217921 is 129712212.

It is not a de Polignac number, because 212217921 - 2² = 212217917 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 7859923 = 212217921 / (2 + 1 + 2 + 2 + 1 + 7 + 9 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (212217991) 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, 3929935 + ... + 3929988.

It is an arithmetic number, because the mean of its divisors is an integer number (39299620).

Almost surely, 2^212217921 is an apocalyptic number.

It is an amenable number.

212217921 is a deficient number, since it is larger than the sum of its proper divisors (102179039).

212217921 is an equidigital number, since it uses as much as digits as its factorization.

212217921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7859932 (or 7859926 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 212217921 is about 14567.7012943017. The cubic root of 212217921 is about 596.4774346947.

The spelling of 212217921 in words is "two hundred twelve million, two hundred seventeen thousand, nine hundred twenty-one".