21131355 has 16 divisors (see below), whose sum is σ = 38640384. Its totient is φ = 9660000.

The previous prime is 21131333. The next prime is 21131389. The reversal of 21131355 is 55313112.

It is not a de Polignac number, because 21131355 - 2⁹ = 21130843 is a prime.

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

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, 100521 + ... + 100730.

It is an arithmetic number, because the mean of its divisors is an integer number (2415024).

Almost surely, 2^21131355 is an apocalyptic number.

21131355 is a deficient number, since it is larger than the sum of its proper divisors (17509029).

21131355 is a wasteful number, since it uses less digits than its factorization.

21131355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 201266.

The product of its digits is 450, while the sum is 21.

The square root of 21131355 is about 4596.8853585879. The cubic root of 21131355 is about 276.4664581130.

Adding to 21131355 its reverse (55313112), we get a palindrome (76444467).

The spelling of 21131355 in words is "twenty-one million, one hundred thirty-one thousand, three hundred fifty-five".