21961802501 has 4 divisors (see below), whose sum is σ = 21962105004. Its totient is φ = 21961500000.

The previous prime is 21961802497. The next prime is 21961802581. The reversal of 21961802501 is 10520816912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 18997108900 + 2964693601 = 137830^2 + 54449^2 .

It is a cyclic number.

It is not a de Polignac number, because 21961802501 - 2² = 21961802497 is a prime.

It is a deceptive number, since it divides R_21961802500.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21961802581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30251 + ... + 211751.

It is an arithmetic number, because the mean of its divisors is an integer number (5490526251).

Almost surely, 2^21961802501 is an apocalyptic number.

21961802501 is the 121001-st pentagonal number.

It is an amenable number.

21961802501 is a deficient number, since it is larger than the sum of its proper divisors (302503).

21961802501 is a wasteful number, since it uses less digits than its factorization.

21961802501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302502.

The product of its (nonzero) digits is 8640, while the sum is 35.

The spelling of 21961802501 in words is "twenty-one billion, nine hundred sixty-one million, eight hundred two thousand, five hundred one".