21715020 has 48 divisors (see below), whose sum is σ = 67559520. Its totient is φ = 5790528.

The previous prime is 21715007. The next prime is 21715049. The reversal of 21715020 is 2051712.

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

It is a junction number, because it is equal to n+sod(n) for n = 21714984 and 21715002.

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 15 ways as a sum of consecutive naturals, for example, 19567 + ... + 20646.

It is an arithmetic number, because the mean of its divisors is an integer number (1407490).

Almost surely, 2^21715020 is an apocalyptic number.

21715020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21715020 is an abundant number, since it is smaller than the sum of its proper divisors (45844500).

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

21715020 is a wasteful number, since it uses less digits than its factorization.

21715020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40231 (or 40223 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21715020 is about 4659.9377678248. The cubic root of 21715020 is about 278.9887843798.

Adding to 21715020 its reverse (2051712), we get a palindrome (23766732).

The spelling of 21715020 in words is "twenty-one million, seven hundred fifteen thousand, twenty".