21651404518 has 4 divisors (see below), whose sum is σ = 32477106780. Its totient is φ = 10825702258.

The previous prime is 21651404503. The next prime is 21651404519. The reversal of 21651404518 is 81540415612.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651404519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5412851128 + ... + 5412851131.

It is an arithmetic number, because the mean of its divisors is an integer number (8119276695).

Almost surely, 2^21651404518 is an apocalyptic number.

21651404518 is a deficient number, since it is larger than the sum of its proper divisors (10825702262).

21651404518 is a wasteful number, since it uses less digits than its factorization.

21651404518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10825702261.

The product of its (nonzero) digits is 38400, while the sum is 37.

The spelling of 21651404518 in words is "twenty-one billion, six hundred fifty-one million, four hundred four thousand, five hundred eighteen".