21006562709 has 16 divisors (see below), whose sum is σ = 23255796480. Its totient is φ = 18814498560.

The previous prime is 21006562691. The next prime is 21006562727. The reversal of 21006562709 is 90726560012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21006562691) and next prime (21006562727).

It is not a de Polignac number, because 21006562709 - 2²⁸ = 20738127253 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006562739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 738452 + ... + 766370.

It is an arithmetic number, because the mean of its divisors is an integer number (1453487280).

Almost surely, 2^21006562709 is an apocalyptic number.

It is an amenable number.

21006562709 is a deficient number, since it is larger than the sum of its proper divisors (2249233771).

21006562709 is a wasteful number, since it uses less digits than its factorization.

21006562709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28940.

The product of its (nonzero) digits is 45360, while the sum is 38.

The spelling of 21006562709 in words is "twenty-one billion, six million, five hundred sixty-two thousand, seven hundred nine".