21487693 has 2 divisors, whose sum is σ = 21487694. Its totient is φ = 21487692.

The previous prime is 21487673. The next prime is 21487699. The reversal of 21487693 is 39678412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20412324 + 1075369 = 4518^2 + 1037^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21487693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21487699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10743846 + 10743847.

It is an arithmetic number, because the mean of its divisors is an integer number (10743847).

Almost surely, 2^21487693 is an apocalyptic number.

It is an amenable number.

21487693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21487693 is an equidigital number, since it uses as much as digits as its factorization.

21487693 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 21487693 is about 4635.4819598398. The cubic root of 21487693 is about 278.0118216942.

The spelling of 21487693 in words is "twenty-one million, four hundred eighty-seven thousand, six hundred ninety-three".