21136897 has 4 divisors (see below), whose sum is σ = 21150036. Its totient is φ = 21123760.

The previous prime is 21136891. The next prime is 21136903. The reversal of 21136897 is 79863112.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21136891) and next prime (21136903).

It can be written as a sum of positive squares in 2 ways, for example, as 18284176 + 2852721 = 4276^2 + 1689^2 .

It is a cyclic number.

It is not a de Polignac number, because 21136897 - 2⁷ = 21136769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21136891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3754 + ... + 7507.

It is an arithmetic number, because the mean of its divisors is an integer number (5287509).

Almost surely, 2^21136897 is an apocalyptic number.

21136897 is the 3754-th pentagonal number.

It is an amenable number.

21136897 is a deficient number, since it is larger than the sum of its proper divisors (13139).

21136897 is a wasteful number, since it uses less digits than its factorization.

21136897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13138.

The product of its digits is 18144, while the sum is 37.

The square root of 21136897 is about 4597.4881185273. The cubic root of 21136897 is about 276.4906250943.

The spelling of 21136897 in words is "twenty-one million, one hundred thirty-six thousand, eight hundred ninety-seven".