721943021 has 4 divisors (see below), whose sum is σ = 753331872. Its totient is φ = 690554172.

The previous prime is 721942999. The next prime is 721943071. The reversal of 721943021 is 120349127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 721943021 - 2⁶ = 721942957 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 (721943071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15694391 + ... + 15694436.

It is an arithmetic number, because the mean of its divisors is an integer number (188332968).

Almost surely, 2^721943021 is an apocalyptic number.

It is an amenable number.

721943021 is a deficient number, since it is larger than the sum of its proper divisors (31388851).

721943021 is a wasteful number, since it uses less digits than its factorization.

721943021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31388850.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 721943021 is about 26868.9973947671. The cubic root of 721943021 is about 897.0864717636.

The spelling of 721943021 in words is "seven hundred twenty-one million, nine hundred forty-three thousand, twenty-one".