21051551394 has 12 divisors (see below), whose sum is σ = 45611694726. Its totient is φ = 7017183792.

The previous prime is 21051551387. The next prime is 21051551447. The reversal of 21051551394 is 49315515012.

It is a happy number.

21051551394 is a `hidden beast` number, since 2 + 1 + 0 + 51 + 5 + 513 + 94 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14649471225 + 6402080169 = 121035^2 + 80013^2 .

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 584765299 + ... + 584765334.

Almost surely, 2^21051551394 is an apocalyptic number.

21051551394 is an abundant number, since it is smaller than the sum of its proper divisors (24560143332).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21051551394 is a wasteful number, since it uses less digits than its factorization.

21051551394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1169530641 (or 1169530638 counting only the distinct ones).

The product of its (nonzero) digits is 27000, while the sum is 36.

The spelling of 21051551394 in words is "twenty-one billion, fifty-one million, five hundred fifty-one thousand, three hundred ninety-four".