21355131 has 24 divisors (see below), whose sum is σ = 33759504. Its totient is φ = 11968320.

The previous prime is 21355121. The next prime is 21355151. The reversal of 21355131 is 13155312.

It is not a de Polignac number, because 21355131 - 2⁷ = 21355003 is a prime.

It is a super-2 number, since 2×21355131² = 912083240054322, which contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 21355098 and 21355107.

It is not an unprimeable number, because it can be changed into a prime (21355121) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6421 + ... + 9161.

It is an arithmetic number, because the mean of its divisors is an integer number (1406646).

Almost surely, 2^21355131 is an apocalyptic number.

21355131 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21355131 is a deficient number, since it is larger than the sum of its proper divisors (12404373).

21355131 is a wasteful number, since it uses less digits than its factorization.

21355131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2811 (or 2804 counting only the distinct ones).

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

The square root of 21355131 is about 4621.1612177028. The cubic root of 21355131 is about 277.4389379485.

The spelling of 21355131 in words is "twenty-one million, three hundred fifty-five thousand, one hundred thirty-one".