721997387 has 4 divisors (see below), whose sum is σ = 724661856. Its totient is φ = 719332920.

The previous prime is 721997351. The next prime is 721997417. The reversal of 721997387 is 783799127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 783799127 = 17 ⋅46105831.

It is a cyclic number.

It is not a de Polignac number, because 721997387 - 2¹² = 721993291 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721993387) 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, 1331828 + ... + 1332369.

It is an arithmetic number, because the mean of its divisors is an integer number (181165464).

Almost surely, 2^721997387 is an apocalyptic number.

721997387 is a deficient number, since it is larger than the sum of its proper divisors (2664469).

721997387 is a wasteful number, since it uses less digits than its factorization.

721997387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2664468.

The product of its digits is 1333584, while the sum is 53.

The square root of 721997387 is about 26870.0090621496. The cubic root of 721997387 is about 897.1089895974.

The spelling of 721997387 in words is "seven hundred twenty-one million, nine hundred ninety-seven thousand, three hundred eighty-seven".