21156117840 has 1200 divisors, whose sum is σ = 92861556480. Its totient is φ = 4399349760.

The previous prime is 21156117833. The next prime is 21156117847. The reversal of 21156117840 is 4871165112.

21156117840 is a `hidden beast` number, since 2 + 1 + 1 + 561 + 17 + 84 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21156117833) and next prime (21156117847).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21156117795 and 21156117804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21156117847) by changing a digit.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 267798921 + ... + 267798999.

Almost surely, 2^21156117840 is an apocalyptic number.

21156117840 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 21156117840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46430778240).

21156117840 is an abundant number, since it is smaller than the sum of its proper divisors (71705438640).

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

21156117840 is a wasteful number, since it uses less digits than its factorization.

21156117840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The spelling of 21156117840 in words is "twenty-one billion, one hundred fifty-six million, one hundred seventeen thousand, eight hundred forty".