21681510 has 32 divisors (see below), whose sum is σ = 52224480. Its totient is φ = 5760768.

The previous prime is 21681487. The next prime is 21681529. The reversal of 21681510 is 1518612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8236 + ... + 10544.

It is an arithmetic number, because the mean of its divisors is an integer number (1632015).

Almost surely, 2^21681510 is an apocalyptic number.

21681510 is an abundant number, since it is smaller than the sum of its proper divisors (30542970).

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

21681510 is a wasteful number, since it uses less digits than its factorization.

21681510 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2632.

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 21681510 is about 4656.3408380401. The cubic root of 21681510 is about 278.8452013163.

The spelling of 21681510 in words is "twenty-one million, six hundred eighty-one thousand, five hundred ten".