21691003 has 2 divisors, whose sum is σ = 21691004. Its totient is φ = 21691002.

The previous prime is 21690983. The next prime is 21691013. The reversal of 21691003 is 30019612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21691003 - 2²¹ = 19593851 is a prime.

It is a super-2 number, since 2×21691003² = 940999222292018, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21691013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10845501 + 10845502.

It is an arithmetic number, because the mean of its divisors is an integer number (10845502).

Almost surely, 2^21691003 is an apocalyptic number.

21691003 is a deficient number, since it is larger than the sum of its proper divisors (1).

21691003 is an equidigital number, since it uses as much as digits as its factorization.

21691003 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 324, while the sum is 22.

The square root of 21691003 is about 4657.3600891492. The cubic root of 21691003 is about 278.8858917673.

It can be divided in two parts, 216 and 91003, that added together give a palindrome (91219).

The spelling of 21691003 in words is "twenty-one million, six hundred ninety-one thousand, three".