21555137747 has 32 divisors (see below), whose sum is σ = 26107510464. Its totient is φ = 17533900800.

The previous prime is 21555137741. The next prime is 21555137749. The reversal of 21555137747 is 74773155512.

It is not a de Polignac number, because 21555137747 - 2³⁰ = 20481395923 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21555137741) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 908783 + ... + 932199.

It is an arithmetic number, because the mean of its divisors is an integer number (815859702).

Almost surely, 2^21555137747 is an apocalyptic number.

21555137747 is a deficient number, since it is larger than the sum of its proper divisors (4552372717).

21555137747 is a wasteful number, since it uses less digits than its factorization.

21555137747 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23639.

The product of its digits is 1029000, while the sum is 47.

The spelling of 21555137747 in words is "twenty-one billion, five hundred fifty-five million, one hundred thirty-seven thousand, seven hundred forty-seven".