21097481 has 2 divisors, whose sum is σ = 21097482. Its totient is φ = 21097480.

The previous prime is 21097469. The next prime is 21097487. The reversal of 21097481 is 18479012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18139081 + 2958400 = 4259^2 + 1720^2 .

It is a cyclic number.

It is not a de Polignac number, because 21097481 - 2¹⁰ = 21096457 is a prime.

It is a super-2 number, since 2×21097481² = 890207409090722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21097487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10548740 + 10548741.

It is an arithmetic number, because the mean of its divisors is an integer number (10548741).

Almost surely, 2^21097481 is an apocalyptic number.

It is an amenable number.

21097481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21097481 is an equidigital number, since it uses as much as digits as its factorization.

21097481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21097481 is about 4593.1994295915. The cubic root of 21097481 is about 276.3186519520.

The spelling of 21097481 in words is "twenty-one million, ninety-seven thousand, four hundred eighty-one".