21720050 has 96 divisors (see below), whose sum is σ = 49175424. Its totient is φ = 7040000.

The previous prime is 21720047. The next prime is 21720053. The reversal of 21720050 is 5002712.

It is an interprime number because it is at equal distance from previous prime (21720047) and next prime (21720053).

It is a Harshad number since it is a multiple of its sum of digits (17).

It is not an unprimeable number, because it can be changed into a prime (21720053) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 215000 + ... + 215100.

It is an arithmetic number, because the mean of its divisors is an integer number (512244).

Almost surely, 2^21720050 is an apocalyptic number.

21720050 is an abundant number, since it is smaller than the sum of its proper divisors (27455374).

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

21720050 is a wasteful number, since it uses less digits than its factorization.

21720050 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164 (or 159 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 21720050 is about 4660.4774433528. The cubic root of 21720050 is about 279.0103240828.

Adding to 21720050 its reverse (5002712), we get a palindrome (26722762).

The spelling of 21720050 in words is "twenty-one million, seven hundred twenty thousand, fifty".