21531601440 has 240 divisors, whose sum is σ = 76703723712. Its totient is φ = 5687732736.

The previous prime is 21531601391. The next prime is 21531601489. The reversal of 21531601440 is 4410613512.

It is a happy number.

21531601440 is a `hidden beast` number, since 2 + 1 + 53 + 1 + 601 + 4 + 4 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21531601391) and next prime (21531601489).

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1378957 + ... + 1394483.

Almost surely, 2^21531601440 is an apocalyptic number.

21531601440 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 21531601440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38351861856).

21531601440 is an abundant number, since it is smaller than the sum of its proper divisors (55172122272).

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

21531601440 is a wasteful number, since it uses less digits than its factorization.

21531601440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15661 (or 15644 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 27.

The spelling of 21531601440 in words is "twenty-one billion, five hundred thirty-one million, six hundred one thousand, four hundred forty".