21525640 has 32 divisors (see below), whose sum is σ = 48600000. Its totient is φ = 8580544.

The previous prime is 21525571. The next prime is 21525641. The reversal of 21525640 is 4652512.

It is not an unprimeable number, because it can be changed into a prime (21525641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13611 + ... + 15109.

It is an arithmetic number, because the mean of its divisors is an integer number (1518750).

Almost surely, 2^21525640 is an apocalyptic number.

21525640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21525640 is an abundant number, since it is smaller than the sum of its proper divisors (27074360).

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

21525640 is a wasteful number, since it uses less digits than its factorization.

21525640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1869 (or 1865 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 21525640 is about 4639.5732562381. The cubic root of 21525640 is about 278.1753805968.

It can be divided in two parts, 215256 and 40, that added together give a square (215296 = 464²).

The spelling of 21525640 in words is "twenty-one million, five hundred twenty-five thousand, six hundred forty".