21499477129 has 9 divisors (see below), whose sum is σ = 23282563143. Its totient is φ = 19843911672.

The previous prime is 21499477123. The next prime is 21499477141. The reversal of 21499477129 is 92177499412.

It is a happy number.

The square root of 21499477129 is 146627.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 3180396025 + 18319081104 = 56395^2 + 135348^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21499477129 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21499477129.

It is not an unprimeable number, because it can be changed into a prime (21499477123) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1900512 + ... + 1911790.

Almost surely, 2^21499477129 is an apocalyptic number.

21499477129 is the 146627-th square number.

21499477129 is the 73314-th centered octagonal number.

It is an amenable number.

21499477129 is a deficient number, since it is larger than the sum of its proper divisors (1783086014).

21499477129 is an frugal number, since it uses more digits than its factorization.

21499477129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22584 (or 11292 counting only the distinct ones).

The product of its digits is 2286144, while the sum is 55.

The spelling of 21499477129 in words is "twenty-one billion, four hundred ninety-nine million, four hundred seventy-seven thousand, one hundred twenty-nine".