21520460 has 36 divisors (see below), whose sum is σ = 48944448. Its totient is φ = 7944768.

The previous prime is 21520459. The next prime is 21520463. The reversal of 21520460 is 6402512.

It is a happy number.

It is a super-2 number, since 2×21520460² = 926260397223200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is not an unprimeable number, because it can be changed into a prime (21520463) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 197 + ... + 6563.

It is an arithmetic number, because the mean of its divisors is an integer number (1359568).

Almost surely, 2^21520460 is an apocalyptic number.

21520460 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 21520460, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24472224).

21520460 is an abundant number, since it is smaller than the sum of its proper divisors (27423988).

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

21520460 is a wasteful number, since it uses less digits than its factorization.

21520460 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6402 (or 6387 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21520460 is about 4639.0149816529. The cubic root of 21520460 is about 278.1530651307.

Adding to 21520460 its reverse (6402512), we get a palindrome (27922972).

The spelling of 21520460 in words is "twenty-one million, five hundred twenty thousand, four hundred sixty".