21746721501 has 6 divisors (see below), whose sum is σ = 31411931070. Its totient is φ = 14497814328.

The previous prime is 21746721461. The next prime is 21746721509. The reversal of 21746721501 is 10512764712.

21746721501 is a `hidden beast` number, since 2 + 1 + 74 + 67 + 21 + 501 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21144068100 + 602653401 = 145410^2 + 24549^2 .

It is not a de Polignac number, because 21746721501 - 2¹³ = 21746713309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21746721509) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1208151186 + ... + 1208151203.

It is an arithmetic number, because the mean of its divisors is an integer number (5235321845).

Almost surely, 2^21746721501 is an apocalyptic number.

It is an amenable number.

21746721501 is a deficient number, since it is larger than the sum of its proper divisors (9665209569).

21746721501 is a wasteful number, since it uses less digits than its factorization.

21746721501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2416302395 (or 2416302392 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The spelling of 21746721501 in words is "twenty-one billion, seven hundred forty-six million, seven hundred twenty-one thousand, five hundred one".