21117620 has 12 divisors (see below), whose sum is σ = 44347044. Its totient is φ = 8447040.

The previous prime is 21117563. The next prime is 21117631. The reversal of 21117620 is 2671112.

It can be written as a sum of positive squares in 2 ways, for example, as 10903204 + 10214416 = 3302^2 + 3196^2 .

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1055881 = 21117620 / (2 + 1 + 1 + 1 + 7 + 6 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 21117592 and 21117601.

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 527921 + ... + 527960.

It is an arithmetic number, because the mean of its divisors is an integer number (3695587).

Almost surely, 2^21117620 is an apocalyptic number.

21117620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21117620 is an abundant number, since it is smaller than the sum of its proper divisors (23229424).

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

21117620 is a wasteful number, since it uses less digits than its factorization.

21117620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1055890 (or 1055888 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 20.

The square root of 21117620 is about 4595.3911694218. The cubic root of 21117620 is about 276.4065457250.

Adding to 21117620 its reverse (2671112), we get a palindrome (23788732).

The spelling of 21117620 in words is "twenty-one million, one hundred seventeen thousand, six hundred twenty".