391381616025 has 81 divisors (see below), whose sum is σ = 707984589949. Its totient is φ = 206679872640.

The previous prime is 391381615991. The next prime is 391381616033. The reversal of 391381616025 is 520616183193.

The square root of 391381616025 is 625605.

It is a perfect power (a square), and thus also a powerful number.

391381616025 is a `hidden beast` number, since 3 + 9 + 1 + 3 + 8 + 1 + 616 + 0 + 25 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 77077861641 + 314303754384 = 277629^2 + 560628^2 .

It is not a de Polignac number, because 391381616025 - 2³⁷ = 253942662553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 1679749309 + ... + 1679749541.

Almost surely, 2^391381616025 is an apocalyptic number.

391381616025 is the 625605-th square number.

391381616025 is the 312803-rd centered octagonal number.

It is an amenable number.

391381616025 is a deficient number, since it is larger than the sum of its proper divisors (316602973924).

391381616025 is an equidigital number, since it uses as much as digits as its factorization.

391381616025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840 (or 420 counting only the distinct ones).

The product of its (nonzero) digits is 233280, while the sum is 45.

The spelling of 391381616025 in words is "three hundred ninety-one billion, three hundred eighty-one million, six hundred sixteen thousand, twenty-five".