406217721 has 16 divisors (see below), whose sum is σ = 666614144. Its totient is φ = 214268544.

The previous prime is 406217699. The next prime is 406217723. The reversal of 406217721 is 127712604.

It is not a de Polignac number, because 406217721 - 2¹⁴ = 406201337 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (406217723) 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, 743716 + ... + 744261.

It is an arithmetic number, because the mean of its divisors is an integer number (41663384).

Almost surely, 2^406217721 is an apocalyptic number.

It is an amenable number.

406217721 is a deficient number, since it is larger than the sum of its proper divisors (260396423).

406217721 is a wasteful number, since it uses less digits than its factorization.

406217721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1488000.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 406217721 is about 20154.8436114002. The cubic root of 406217721 is about 740.6044009083.

The spelling of 406217721 in words is "four hundred six million, two hundred seventeen thousand, seven hundred twenty-one".