21021131 has 4 divisors (see below), whose sum is σ = 21699264. Its totient is φ = 20343000.

The previous prime is 21021127. The next prime is 21021157. The reversal of 21021131 is 13112012.

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 21021131 - 2² = 21021127 is a prime.

It is a super-2 number, since 2×21021131² = 883775897038322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21021101) 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, 339020 + ... + 339081.

It is an arithmetic number, because the mean of its divisors is an integer number (5424816).

Almost surely, 2^21021131 is an apocalyptic number.

21021131 is a deficient number, since it is larger than the sum of its proper divisors (678133).

21021131 is an equidigital number, since it uses as much as digits as its factorization.

21021131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 678132.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21021131 is about 4584.8806963759. The cubic root of 21021131 is about 275.9849244374.

Adding to 21021131 its reverse (13112012), we get a palindrome (34133143).

The spelling of 21021131 in words is "twenty-one million, twenty-one thousand, one hundred thirty-one".