21172620 has 48 divisors (see below), whose sum is σ = 67753728. Its totient is φ = 4839360.

The previous prime is 21172601. The next prime is 21172637. The reversal of 21172620 is 2627112.

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24786 + ... + 25625.

It is an arithmetic number, because the mean of its divisors is an integer number (1411536).

Almost surely, 2^21172620 is an apocalyptic number.

21172620 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21172620 is an abundant number, since it is smaller than the sum of its proper divisors (46581108).

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

21172620 is a wasteful number, since it uses less digits than its factorization.

21172620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50430 (or 50428 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 21172620 is about 4601.3715346622. The cubic root of 21172620 is about 276.6463009799.

Adding to 21172620 its reverse (2627112), we get a palindrome (23799732).

The spelling of 21172620 in words is "twenty-one million, one hundred seventy-two thousand, six hundred twenty".