21513197 has 2 divisors, whose sum is σ = 21513198. Its totient is φ = 21513196.

The previous prime is 21513181. The next prime is 21513203. The reversal of 21513197 is 79131512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21058921 + 454276 = 4589^2 + 674^2 .

It is a cyclic number.

It is not a de Polignac number, because 21513197 - 2⁴ = 21513181 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21513127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756598 + 10756599.

It is an arithmetic number, because the mean of its divisors is an integer number (10756599).

Almost surely, 2^21513197 is an apocalyptic number.

It is an amenable number.

21513197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513197 is an equidigital number, since it uses as much as digits as its factorization.

21513197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1890, while the sum is 29.

The square root of 21513197 is about 4638.2320985479. The cubic root of 21513197 is about 278.1217700589.

The spelling of 21513197 in words is "twenty-one million, five hundred thirteen thousand, one hundred ninety-seven".