787638721 has 8 divisors (see below), whose sum is σ = 809627240. Its totient is φ = 765687168.

The previous prime is 787638707. The next prime is 787638727. The reversal of 787638721 is 127836787.

It can be written as a sum of positive squares in 4 ways, for example, as 351037696 + 436601025 = 18736^2 + 20895^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 787638721 - 2²¹ = 785541569 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (787638727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37165 + ... + 54373.

It is an arithmetic number, because the mean of its divisors is an integer number (101203405).

Almost surely, 2^787638721 is an apocalyptic number.

It is an amenable number.

787638721 is a deficient number, since it is larger than the sum of its proper divisors (21988519).

787638721 is a wasteful number, since it uses less digits than its factorization.

787638721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18483.

The product of its digits is 790272, while the sum is 49.

The square root of 787638721 is about 28064.9019417492. The cubic root of 787638721 is about 923.5115955030.

The spelling of 787638721 in words is "seven hundred eighty-seven million, six hundred thirty-eight thousand, seven hundred twenty-one".