21503693 has 2 divisors, whose sum is σ = 21503694. Its totient is φ = 21503692.

The previous prime is 21503653. The next prime is 21503719. The reversal of 21503693 is 39630512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17123044 + 4380649 = 4138^2 + 2093^2 .

It is a cyclic number.

It is not a de Polignac number, because 21503693 - 2⁸ = 21503437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21503653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10751846 + 10751847.

It is an arithmetic number, because the mean of its divisors is an integer number (10751847).

Almost surely, 2^21503693 is an apocalyptic number.

It is an amenable number.

21503693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21503693 is an equidigital number, since it uses as much as digits as its factorization.

21503693 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21503693 is about 4637.2074570802. The cubic root of 21503693 is about 278.0808082461.

The spelling of 21503693 in words is "twenty-one million, five hundred three thousand, six hundred ninety-three".