21511854 has 96 divisors (see below), whose sum is σ = 59963904. Its totient is φ = 5417280.

The previous prime is 21511849. The next prime is 21511871. The reversal of 21511854 is 45811512.

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 47 ways as a sum of consecutive naturals, for example, 37389 + ... + 37959.

It is an arithmetic number, because the mean of its divisors is an integer number (624624).

Almost surely, 2^21511854 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21511854, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29981952).

21511854 is an abundant number, since it is smaller than the sum of its proper divisors (38452050).

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

21511854 is a wasteful number, since it uses less digits than its factorization.

21511854 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 622 (or 619 counting only the distinct ones).

The product of its digits is 1600, while the sum is 27.

The square root of 21511854 is about 4638.0873212996. The cubic root of 21511854 is about 278.1159825213.

It can be divided in two parts, 2151 and 1854, that added together give a triangular number (4005 = T₈₉).

The spelling of 21511854 in words is "twenty-one million, five hundred eleven thousand, eight hundred fifty-four".