87638389721 has 2 divisors, whose sum is σ = 87638389722. Its totient is φ = 87638389720.

The previous prime is 87638389717. The next prime is 87638389771. The reversal of 87638389721 is 12798383678.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69097482496 + 18540907225 = 262864^2 + 136165^2 .

It is a cyclic number.

It is not a de Polignac number, because 87638389721 - 2² = 87638389717 is a prime.

It is not a weakly prime, because it can be changed into another prime (87638389771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43819194860 + 43819194861.

It is an arithmetic number, because the mean of its divisors is an integer number (43819194861).

Almost surely, 2^87638389721 is an apocalyptic number.

It is an amenable number.

87638389721 is a deficient number, since it is larger than the sum of its proper divisors (1).

87638389721 is an equidigital number, since it uses as much as digits as its factorization.

87638389721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24385536, while the sum is 62.

The spelling of 87638389721 in words is "eighty-seven billion, six hundred thirty-eight million, three hundred eighty-nine thousand, seven hundred twenty-one".