721381057 has 4 divisors (see below), whose sum is σ = 722503600. Its totient is φ = 720258516.

The previous prime is 721381021. The next prime is 721381099. The reversal of 721381057 is 750183127.

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, and also an emirpimes, since its reverse is a distinct semiprime: 750183127 = 499 ⋅1503373.

It is a cyclic number.

It is not a de Polignac number, because 721381057 - 2¹⁹ = 720856769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721381457) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 560307 + ... + 561592.

It is an arithmetic number, because the mean of its divisors is an integer number (180625900).

Almost surely, 2^721381057 is an apocalyptic number.

It is an amenable number.

721381057 is a deficient number, since it is larger than the sum of its proper divisors (1122543).

721381057 is a wasteful number, since it uses less digits than its factorization.

721381057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1122542.

The product of its (nonzero) digits is 11760, while the sum is 34.

The square root of 721381057 is about 26858.5378790432. The cubic root of 721381057 is about 896.8536458342.

The spelling of 721381057 in words is "seven hundred twenty-one million, three hundred eighty-one thousand, fifty-seven".