21147420 has 72 divisors (see below), whose sum is σ = 68889744. Its totient is φ = 4833024.

The previous prime is 21147397. The next prime is 21147433. The reversal of 21147420 is 2474112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 657 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (956802).

Almost surely, 2^21147420 is an apocalyptic number.

21147420 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 21147420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34444872).

21147420 is an abundant number, since it is smaller than the sum of its proper divisors (47742324).

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

21147420 is a wasteful number, since it uses less digits than its factorization.

21147420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7219 (or 7210 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21147420 is about 4598.6324054005. The cubic root of 21147420 is about 276.5365010831.

The spelling of 21147420 in words is "twenty-one million, one hundred forty-seven thousand, four hundred twenty".