21006440947 has 2 divisors, whose sum is σ = 21006440948. Its totient is φ = 21006440946.

The previous prime is 21006440927. The next prime is 21006440963. The reversal of 21006440947 is 74904460012.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21006440947 - 2¹¹ = 21006438899 is a prime.

It is a super-2 number, since 2×21006440947² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21006440927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503220473 + 10503220474.

It is an arithmetic number, because the mean of its divisors is an integer number (10503220474).

Almost surely, 2^21006440947 is an apocalyptic number.

21006440947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006440947 is an equidigital number, since it uses as much as digits as its factorization.

21006440947 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48384, while the sum is 37.

The spelling of 21006440947 in words is "twenty-one billion, six million, four hundred forty thousand, nine hundred forty-seven".