21954640 has 40 divisors (see below), whose sum is σ = 52139520. Its totient is φ = 8593536.

The previous prime is 21954631. The next prime is 21954643. The reversal of 21954640 is 4645912.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21954643) 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, 841 + ... + 6679.

It is an arithmetic number, because the mean of its divisors is an integer number (1303488).

Almost surely, 2^21954640 is an apocalyptic number.

21954640 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 21954640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26069760).

21954640 is an abundant number, since it is smaller than the sum of its proper divisors (30184880).

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

21954640 is a wasteful number, since it uses less digits than its factorization.

21954640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5899 (or 5893 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21954640 is about 4685.5778725788. The cubic root of 21954640 is about 280.0112240399.

The spelling of 21954640 in words is "twenty-one million, nine hundred fifty-four thousand, six hundred forty".