21361840 has 40 divisors (see below), whose sum is σ = 49907520. Its totient is φ = 8503296.

The previous prime is 21361831. The next prime is 21361853. The reversal of 21361840 is 4816312.

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20041 + ... + 21079.

It is an arithmetic number, because the mean of its divisors is an integer number (1247688).

Almost surely, 2^21361840 is an apocalyptic number.

21361840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21361840 is an abundant number, since it is smaller than the sum of its proper divisors (28545680).

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

21361840 is a wasteful number, since it uses less digits than its factorization.

21361840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1309 (or 1303 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21361840 is about 4621.8870604981. The cubic root of 21361840 is about 277.4679886241.

It can be divided in two parts, 21361 and 840, that added together give a square (22201 = 149²).

The spelling of 21361840 in words is "twenty-one million, three hundred sixty-one thousand, eight hundred forty".