21415002543551 has 4 divisors (see below), whose sum is σ = 22542107940600. Its totient is φ = 20287897146504.

The previous prime is 21415002543503. The next prime is 21415002543587. The reversal of 21415002543551 is 15534520051412.

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

It is a cyclic number.

It is not a de Polignac number, because 21415002543551 - 2³⁸ = 21140124636607 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21415002548551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 563552698496 + ... + 563552698533.

It is an arithmetic number, because the mean of its divisors is an integer number (5635526985150).

Almost surely, 2^{21415002543551} is an apocalyptic number.

21415002543551 is a deficient number, since it is larger than the sum of its proper divisors (1127105397049).

21415002543551 is a wasteful number, since it uses less digits than its factorization.

21415002543551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127105397048.

The product of its (nonzero) digits is 120000, while the sum is 38.

Adding to 21415002543551 its reverse (15534520051412), we get a palindrome (36949522594963).

The spelling of 21415002543551 in words is "twenty-one trillion, four hundred fifteen billion, two million, five hundred forty-three thousand, five hundred fifty-one".