21531953 has 2 divisors, whose sum is σ = 21531954. Its totient is φ = 21531952.

The previous prime is 21531947. The next prime is 21531967. The reversal of 21531953 is 35913512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21418384 + 113569 = 4628^2 + 337^2 .

It is a cyclic number.

It is not a de Polignac number, because 21531953 - 2⁶ = 21531889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21531973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765976 + 10765977.

It is an arithmetic number, because the mean of its divisors is an integer number (10765977).

Almost surely, 2^21531953 is an apocalyptic number.

It is an amenable number.

21531953 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531953 is an equidigital number, since it uses as much as digits as its factorization.

21531953 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4050, while the sum is 29.

The square root of 21531953 is about 4640.2535491070. The cubic root of 21531953 is about 278.2025721930.

The spelling of 21531953 in words is "twenty-one million, five hundred thirty-one thousand, nine hundred fifty-three".