21551693 has 2 divisors, whose sum is σ = 21551694. Its totient is φ = 21551692.

The previous prime is 21551671. The next prime is 21551701. The reversal of 21551693 is 39615512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20268004 + 1283689 = 4502^2 + 1133^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551693 - 2¹⁴ = 21535309 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21551623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775846 + 10775847.

It is an arithmetic number, because the mean of its divisors is an integer number (10775847).

Almost surely, 2^21551693 is an apocalyptic number.

It is an amenable number.

21551693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551693 is an equidigital number, since it uses as much as digits as its factorization.

21551693 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8100, while the sum is 32.

The square root of 21551693 is about 4642.3801007673. The cubic root of 21551693 is about 278.2875628021.

The spelling of 21551693 in words is "twenty-one million, five hundred fifty-one thousand, six hundred ninety-three".