21510052020 has 36 divisors (see below), whose sum is σ = 65247158340. Its totient is φ = 5736013824.

The previous prime is 21510052001. The next prime is 21510052049. The reversal of 21510052020 is 2025001512.

21510052020 is a `hidden beast` number, since 21 + 5 + 100 + 520 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15008210064 + 6501841956 = 122508^2 + 80634^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21510051984 and 21510052002.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59749965 + ... + 59750324.

It is an arithmetic number, because the mean of its divisors is an integer number (1812421065).

Almost surely, 2^21510052020 is an apocalyptic number.

21510052020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21510052020 is an abundant number, since it is smaller than the sum of its proper divisors (43737106320).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21510052020 is a wasteful number, since it uses less digits than its factorization.

21510052020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119500304 (or 119500299 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

Adding to 21510052020 its reverse (2025001512), we get a palindrome (23535053532).

The spelling of 21510052020 in words is "twenty-one billion, five hundred ten million, fifty-two thousand, twenty".