21000015706 has 4 divisors (see below), whose sum is σ = 31500023562. Its totient is φ = 10500007852.

The previous prime is 21000015689. The next prime is 21000015709. The reversal of 21000015706 is 60751000012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 15610253481 + 5389762225 = 124941^2 + 73415^2 .

It is not an unprimeable number, because it can be changed into a prime (21000015709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250003925 + ... + 5250003928.

Almost surely, 2^21000015706 is an apocalyptic number.

21000015706 is a deficient number, since it is larger than the sum of its proper divisors (10500007856).

21000015706 is a wasteful number, since it uses less digits than its factorization.

21000015706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10500007855.

The product of its (nonzero) digits is 420, while the sum is 22.

Adding to 21000015706 its reverse (60751000012), we get a palindrome (81751015718).

The spelling of 21000015706 in words is "twenty-one billion, fifteen thousand, seven hundred six".