721667421 has 8 divisors (see below), whose sum is σ = 1069136960. Its totient is φ = 481111596.

The previous prime is 721667417. The next prime is 721667423. The reversal of 721667421 is 124766127.

721667421 is a `hidden beast` number, since 72 + 166 + 7 + 421 = 666.

721667421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 721667421 - 2² = 721667417 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721667423) 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, 13364185 + ... + 13364238.

It is an arithmetic number, because the mean of its divisors is an integer number (133642120).

Almost surely, 2^721667421 is an apocalyptic number.

It is an amenable number.

721667421 is a deficient number, since it is larger than the sum of its proper divisors (347469539).

721667421 is a wasteful number, since it uses less digits than its factorization.

721667421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26728432 (or 26728426 counting only the distinct ones).

The product of its digits is 28224, while the sum is 36.

The square root of 721667421 is about 26863.8683178726. The cubic root of 721667421 is about 896.9723037052.

The spelling of 721667421 in words is "seven hundred twenty-one million, six hundred sixty-seven thousand, four hundred twenty-one".