721354021 has 2 divisors, whose sum is σ = 721354022. Its totient is φ = 721354020.

The previous prime is 721354003. The next prime is 721354027. The reversal of 721354021 is 120453127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 371140225 + 350213796 = 19265^2 + 18714^2 .

It is an emirp because it is prime and its reverse (120453127) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 721354021 - 2¹³ = 721345829 is a prime.

It is a super-2 number, since 2×721354021² = 1040703247225736882, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721354027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360677010 + 360677011.

It is an arithmetic number, because the mean of its divisors is an integer number (360677011).

Almost surely, 2^721354021 is an apocalyptic number.

It is an amenable number.

721354021 is a deficient number, since it is larger than the sum of its proper divisors (1).

721354021 is an equidigital number, since it uses as much as digits as its factorization.

721354021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 721354021 is about 26858.0345706829. The cubic root of 721354021 is about 896.8424415672.

The spelling of 721354021 in words is "seven hundred twenty-one million, three hundred fifty-four thousand, twenty-one".