21961440 has 144 divisors (see below), whose sum is σ = 76186656. Its totient is φ = 5760000.

The previous prime is 21961427. The next prime is 21961453. The reversal of 21961440 is 4416912.

21961440 is a `hidden beast` number, since 2 + 1 + 9 + 614 + 40 = 666.

It is an interprime number because it is at equal distance from previous prime (21961427) and next prime (21961453).

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 145365 + ... + 145515.

It is an arithmetic number, because the mean of its divisors is an integer number (529074).

Almost surely, 2^21961440 is an apocalyptic number.

21961440 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 21961440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38093328).

21961440 is an abundant number, since it is smaller than the sum of its proper divisors (54225216).

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

21961440 is a wasteful number, since it uses less digits than its factorization.

21961440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273 (or 262 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21961440 is about 4686.3034472812. The cubic root of 21961440 is about 280.0401303026.

The spelling of 21961440 in words is "twenty-one million, nine hundred sixty-one thousand, four hundred forty".