87521821 has 2 divisors, whose sum is σ = 87521822. Its totient is φ = 87521820.

The previous prime is 87521807. The next prime is 87521843. The reversal of 87521821 is 12812578.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73188025 + 14333796 = 8555^2 + 3786^2 .

It is a cyclic number.

It is not a de Polignac number, because 87521821 - 2⁵ = 87521789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (87521851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 43760910 + 43760911.

It is an arithmetic number, because the mean of its divisors is an integer number (43760911).

Almost surely, 2^87521821 is an apocalyptic number.

It is an amenable number.

87521821 is a deficient number, since it is larger than the sum of its proper divisors (1).

87521821 is an equidigital number, since it uses as much as digits as its factorization.

87521821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8960, while the sum is 34.

The square root of 87521821 is about 9355.3097757370. The cubic root of 87521821 is about 443.9889024767.

The spelling of 87521821 in words is "eighty-seven million, five hundred twenty-one thousand, eight hundred twenty-one".