21055501 has 2 divisors, whose sum is σ = 21055502. Its totient is φ = 21055500.

The previous prime is 21055471. The next prime is 21055513. The reversal of 21055501 is 10555012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15760900 + 5294601 = 3970^2 + 2301^2 .

It is a cyclic number.

It is not a de Polignac number, because 21055501 - 2¹⁵ = 21022733 is a prime.

It is a super-2 number, since 2×21055501² = 886668244722002, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21055561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527750 + 10527751.

It is an arithmetic number, because the mean of its divisors is an integer number (10527751).

Almost surely, 2^21055501 is an apocalyptic number.

It is an amenable number.

21055501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21055501 is an equidigital number, since it uses as much as digits as its factorization.

21055501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21055501 is about 4588.6273546672. The cubic root of 21055501 is about 276.1352562919.

The spelling of 21055501 in words is "twenty-one million, fifty-five thousand, five hundred one".