21053531 has 16 divisors (see below), whose sum is σ = 23151744. Its totient is φ = 19065984.

The previous prime is 21053521. The next prime is 21053537. The reversal of 21053531 is 13535012.

It is a cyclic number.

It is not a de Polignac number, because 21053531 - 2⁶ = 21053467 is a prime.

It is a super-2 number, since 2×21053531² = 886502335135922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21053537) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60500 + ... + 60846.

It is an arithmetic number, because the mean of its divisors is an integer number (1446984).

Almost surely, 2^21053531 is an apocalyptic number.

21053531 is a deficient number, since it is larger than the sum of its proper divisors (2098213).

21053531 is a wasteful number, since it uses less digits than its factorization.

21053531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 490.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 21053531 is about 4588.4126885013. The cubic root of 21053531 is about 276.1266440782.

Adding to 21053531 its reverse (13535012), we get a palindrome (34588543).

The spelling of 21053531 in words is "twenty-one million, fifty-three thousand, five hundred thirty-one".