55810021 has 2 divisors, whose sum is σ = 55810022. Its totient is φ = 55810020.

The previous prime is 55809991. The next prime is 55810037. The reversal of 55810021 is 12001855.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50908225 + 4901796 = 7135^2 + 2214^2 .

It is a cyclic number.

It is not a de Polignac number, because 55810021 - 2⁵ = 55809989 is a prime.

It is a super-2 number, since 2×55810021² = 6229516888040882, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 55809974 and 55810001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (55810721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27905010 + 27905011.

It is an arithmetic number, because the mean of its divisors is an integer number (27905011).

Almost surely, 2^55810021 is an apocalyptic number.

It is an amenable number.

55810021 is a deficient number, since it is larger than the sum of its proper divisors (1).

55810021 is an equidigital number, since it uses as much as digits as its factorization.

55810021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 400, while the sum is 22.

The square root of 55810021 is about 7470.6104837557. The cubic root of 55810021 is about 382.1531073984.

Adding to 55810021 its reverse (12001855), we get a palindrome (67811876).

The spelling of 55810021 in words is "fifty-five million, eight hundred ten thousand, twenty-one".