21562640 has 80 divisors (see below), whose sum is σ = 55442880. Its totient is φ = 7733760.

The previous prime is 21562633. The next prime is 21562643. The reversal of 21562640 is 4626512.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (21562643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 94046 + ... + 94274.

It is an arithmetic number, because the mean of its divisors is an integer number (693036).

Almost surely, 2^21562640 is an apocalyptic number.

21562640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21562640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27721440).

21562640 is an abundant number, since it is smaller than the sum of its proper divisors (33880240).

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

21562640 is a wasteful number, since it uses less digits than its factorization.

21562640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360 (or 354 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21562640 is about 4643.5589799205. The cubic root of 21562640 is about 278.3346727638.

The spelling of 21562640 in words is "twenty-one million, five hundred sixty-two thousand, six hundred forty".