406678721 has 2 divisors, whose sum is σ = 406678722. Its totient is φ = 406678720.

The previous prime is 406678703. The next prime is 406678757. The reversal of 406678721 is 127876604.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 285238321 + 121440400 = 16889^2 + 11020^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-406678721 is a prime.

It is a super-2 number, since 2×406678721² = 330775164228391682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (406678781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 203339360 + 203339361.

It is an arithmetic number, because the mean of its divisors is an integer number (203339361).

Almost surely, 2^406678721 is an apocalyptic number.

It is an amenable number.

406678721 is a deficient number, since it is larger than the sum of its proper divisors (1).

406678721 is an equidigital number, since it uses as much as digits as its factorization.

406678721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 112896, while the sum is 41.

The square root of 406678721 is about 20166.2768254331. The cubic root of 406678721 is about 740.8844556167.

The spelling of 406678721 in words is "four hundred six million, six hundred seventy-eight thousand, seven hundred twenty-one".