21375720 has 48 divisors (see below), whose sum is σ = 69472260. Its totient is φ = 5700096.

The previous prime is 21375661. The next prime is 21375721. The reversal of 21375720 is 2757312.

It can be written as a sum of positive squares in 2 ways, for example, as 20738916 + 636804 = 4554^2 + 798^2 .

It is not an unprimeable number, because it can be changed into a prime (21375721) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 29329 + ... + 30048.

Almost surely, 2^21375720 is an apocalyptic number.

21375720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21375720 is an abundant number, since it is smaller than the sum of its proper divisors (48096540).

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

21375720 is a wasteful number, since it uses less digits than its factorization.

21375720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59394 (or 59387 counting only the distinct ones).

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

The square root of 21375720 is about 4623.3883678532. The cubic root of 21375720 is about 277.5280711803.

It can be divided in two parts, 213 and 75720, that multiplied together give a triangular number (16128360 = T₅₆₇₉).

The spelling of 21375720 in words is "twenty-one million, three hundred seventy-five thousand, seven hundred twenty".