21102420 has 24 divisors (see below), whose sum is σ = 59086944. Its totient is φ = 5627296.

The previous prime is 21102409. The next prime is 21102421. The reversal of 21102420 is 2420112.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21102396 and 21102405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21102421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175794 + ... + 175913.

It is an arithmetic number, because the mean of its divisors is an integer number (2461956).

Almost surely, 2^21102420 is an apocalyptic number.

21102420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21102420 is an abundant number, since it is smaller than the sum of its proper divisors (37984524).

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

21102420 is a wasteful number, since it uses less digits than its factorization.

21102420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351719 (or 351717 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 21102420 is about 4593.7370407980. The cubic root of 21102420 is about 276.3402126831.

Adding to 21102420 its reverse (2420112), we get a palindrome (23522532).

The spelling of 21102420 in words is "twenty-one million, one hundred two thousand, four hundred twenty".