55251021 has 16 divisors (see below), whose sum is σ = 86908928. Its totient is φ = 30553200.

The previous prime is 55251017. The next prime is 55251041. The reversal of 55251021 is 12015255.

It is not a de Polignac number, because 55251021 - 2² = 55251017 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55251041) 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 in 15 ways as a sum of consecutive naturals, for example, 41785 + ... + 43086.

It is an arithmetic number, because the mean of its divisors is an integer number (5431808).

Almost surely, 2^55251021 is an apocalyptic number.

It is an amenable number.

55251021 is a deficient number, since it is larger than the sum of its proper divisors (31657907).

55251021 is a wasteful number, since it uses less digits than its factorization.

55251021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84912.

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 55251021 is about 7433.1030532342. The cubic root of 55251021 is about 380.8729262570.

Adding to 55251021 its reverse (12015255), we get a palindrome (67266276).

The spelling of 55251021 in words is "fifty-five million, two hundred fifty-one thousand, twenty-one".