21720375 has 48 divisors (see below), whose sum is σ = 40154400. Its totient is φ = 11289600.

The previous prime is 21720371. The next prime is 21720389. The reversal of 21720375 is 57302712.

It is not a de Polignac number, because 21720375 - 2² = 21720371 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720371) 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, 48151 + ... + 48599.

It is an arithmetic number, because the mean of its divisors is an integer number (836550).

Almost surely, 2^21720375 is an apocalyptic number.

21720375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21720375 is a deficient number, since it is larger than the sum of its proper divisors (18434025).

21720375 is a wasteful number, since it uses less digits than its factorization.

21720375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 513 (or 500 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21720375 is about 4660.5123108946. The cubic root of 21720375 is about 279.0117156987.

The spelling of 21720375 in words is "twenty-one million, seven hundred twenty thousand, three hundred seventy-five".