21315235440 has 160 divisors (see below), whose sum is σ = 68308770816. Its totient is φ = 5492643840.

The previous prime is 21315235423. The next prime is 21315235457. The reversal of 21315235440 is 4453251312.

It is an interprime number because it is at equal distance from previous prime (21315235423) and next prime (21315235457).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21315235398 and 21315235407.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6374409 + ... + 6377751.

Almost surely, 2^21315235440 is an apocalyptic number.

21315235440 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 21315235440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34154385408).

21315235440 is an abundant number, since it is smaller than the sum of its proper divisors (46993535376).

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

21315235440 is a wasteful number, since it uses less digits than its factorization.

21315235440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4247 (or 4241 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 30.

Adding to 21315235440 its reverse (4453251312), we get a palindrome (25768486752).

The spelling of 21315235440 in words is "twenty-one billion, three hundred fifteen million, two hundred thirty-five thousand, four hundred forty".