21021152420 has 24 divisors (see below), whose sum is σ = 44155654200. Its totient is φ = 8406321152.

The previous prime is 21021152413. The next prime is 21021152429. The reversal of 21021152420 is 2425112012.

It can be written as a sum of positive squares in 4 ways, for example, as 5189473444 + 15831678976 = 72038^2 + 125824^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 21021152392 and 21021152401.

It is not an unprimeable number, because it can be changed into a prime (21021152429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 51965 + ... + 211524.

It is an arithmetic number, because the mean of its divisors is an integer number (1839818925).

Almost surely, 2^21021152420 is an apocalyptic number.

21021152420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21021152420 is an abundant number, since it is smaller than the sum of its proper divisors (23134501780).

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

21021152420 is a wasteful number, since it uses less digits than its factorization.

21021152420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267487 (or 267485 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 20.

Adding to 21021152420 its reverse (2425112012), we get a palindrome (23446264432).

The spelling of 21021152420 in words is "twenty-one billion, twenty-one million, one hundred fifty-two thousand, four hundred twenty".