21115710 has 144 divisors (see below), whose sum is σ = 69215328. Its totient is φ = 4371840.

The previous prime is 21115657. The next prime is 21115723. The reversal of 21115710 is 1751112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 76092 + ... + 76368.

It is an arithmetic number, because the mean of its divisors is an integer number (480662).

Almost surely, 2^21115710 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21115710, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34607664).

21115710 is an abundant number, since it is smaller than the sum of its proper divisors (48099618).

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

21115710 is a wasteful number, since it uses less digits than its factorization.

21115710 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319 (or 305 counting only the distinct ones).

The product of its (nonzero) digits is 70, while the sum is 18.

The square root of 21115710 is about 4595.1833478111. The cubic root of 21115710 is about 276.3982122035.

Adding to 21115710 its reverse (1751112), we get a palindrome (22866822).

It can be divided in two parts, 21 and 115710, that multiplied together give a triangular number (2429910 = T₂₂₀₄).

The spelling of 21115710 in words is "twenty-one million, one hundred fifteen thousand, seven hundred ten".