21405220353 has 128 divisors (see below), whose sum is σ = 37920960000. Its totient is φ = 11784683520.

The previous prime is 21405220307. The next prime is 21405220357. The reversal of 21405220353 is 35302250412.

It is a happy number.

21405220353 is a `hidden beast` number, since 2 + 1 + 405 + 2 + 203 + 53 = 666.

It is not a de Polignac number, because 21405220353 - 2⁶ = 21405220289 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21405220357) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 27834753 + ... + 27835521.

It is an arithmetic number, because the mean of its divisors is an integer number (296257500).

Almost surely, 2^21405220353 is an apocalyptic number.

It is an amenable number.

21405220353 is a deficient number, since it is larger than the sum of its proper divisors (16515739647).

21405220353 is a wasteful number, since it uses less digits than its factorization.

21405220353 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 992 (or 986 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 27.

Adding to 21405220353 its reverse (35302250412), we get a palindrome (56707470765).

The spelling of 21405220353 in words is "twenty-one billion, four hundred five million, two hundred twenty thousand, three hundred fifty-three".