100821557 has 2 divisors, whose sum is σ = 100821558. Its totient is φ = 100821556.

The previous prime is 100821551. The next prime is 100821569. The reversal of 100821557 is 755128001.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75881521 + 24940036 = 8711^2 + 4994^2 .

It is a cyclic number.

It is not a de Polignac number, because 100821557 - 2⁶ = 100821493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (100821551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50410778 + 50410779.

It is an arithmetic number, because the mean of its divisors is an integer number (50410779).

Almost surely, 2^100821557 is an apocalyptic number.

It is an amenable number.

100821557 is a deficient number, since it is larger than the sum of its proper divisors (1).

100821557 is an equidigital number, since it uses as much as digits as its factorization.

100821557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2800, while the sum is 29.

The square root of 100821557 is about 10040.9938253143. The cubic root of 100821557 is about 465.4265281309.

Adding to 100821557 its reverse (755128001), we get a palindrome (855949558).

The spelling of 100821557 in words is "one hundred million, eight hundred twenty-one thousand, five hundred fifty-seven".