21551858501 has 2 divisors, whose sum is σ = 21551858502. Its totient is φ = 21551858500.

The previous prime is 21551858453. The next prime is 21551858527. The reversal of 21551858501 is 10585815512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21343749025 + 208109476 = 146095^2 + 14426^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551858501 - 2¹⁰ = 21551857477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21551854501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775929250 + 10775929251.

It is an arithmetic number, because the mean of its divisors is an integer number (10775929251).

Almost surely, 2^21551858501 is an apocalyptic number.

It is an amenable number.

21551858501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551858501 is an equidigital number, since it uses as much as digits as its factorization.

21551858501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 80000, while the sum is 41.

The spelling of 21551858501 in words is "twenty-one billion, five hundred fifty-one million, eight hundred fifty-eight thousand, five hundred one".