21651131 has 4 divisors (see below), whose sum is σ = 21912072. Its totient is φ = 21390192.

The previous prime is 21651121. The next prime is 21651163. The reversal of 21651131 is 13115612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21651131 - 2¹⁸ = 21388987 is a prime.

It is a super-2 number, since 2×21651131² = 937542947158322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21651101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 130346 + ... + 130511.

It is an arithmetic number, because the mean of its divisors is an integer number (5478018).

Almost surely, 2^21651131 is an apocalyptic number.

21651131 is a deficient number, since it is larger than the sum of its proper divisors (260941).

21651131 is an equidigital number, since it uses as much as digits as its factorization.

21651131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 260940.

The product of its digits is 180, while the sum is 20.

The square root of 21651131 is about 4653.0775837074. The cubic root of 21651131 is about 278.7149059964.

Adding to 21651131 its reverse (13115612), we get a palindrome (34766743).

The spelling of 21651131 in words is "twenty-one million, six hundred fifty-one thousand, one hundred thirty-one".