21001131 has 6 divisors (see below), whose sum is σ = 30334980. Its totient is φ = 14000748.

The previous prime is 21001121. The next prime is 21001153. The reversal of 21001131 is 13110012.

It is not a de Polignac number, because 21001131 - 2¹⁸ = 20738987 is a prime.

It is a super-2 number, since 2×21001131² = 882095006558322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2333459 = 21001131 / (2 + 1 + 0 + 0 + 1 + 1 + 3 + 1).

It is not an unprimeable number, because it can be changed into a prime (21001121) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1166721 + ... + 1166738.

It is an arithmetic number, because the mean of its divisors is an integer number (5055830).

Almost surely, 2^21001131 is an apocalyptic number.

21001131 is a deficient number, since it is larger than the sum of its proper divisors (9333849).

21001131 is a wasteful number, since it uses less digits than its factorization.

21001131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2333465 (or 2333462 counting only the distinct ones).

The product of its (nonzero) digits is 6, while the sum is 9.

The square root of 21001131 is about 4582.6990955113. The cubic root of 21001131 is about 275.8973704750.

Adding to 21001131 its reverse (13110012), we get a palindrome (34111143).

The spelling of 21001131 in words is "twenty-one million, one thousand, one hundred thirty-one".