21154551 has 24 divisors (see below), whose sum is σ = 31364592. Its totient is φ = 12672000.

The previous prime is 21154547. The next prime is 21154577. The reversal of 21154551 is 15545112.

It is not a de Polignac number, because 21154551 - 2² = 21154547 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21154591) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36375 + ... + 36951.

It is an arithmetic number, because the mean of its divisors is an integer number (1306858).

Almost surely, 2^21154551 is an apocalyptic number.

21154551 is a deficient number, since it is larger than the sum of its proper divisors (10210041).

21154551 is a wasteful number, since it uses less digits than its factorization.

21154551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 703 (or 692 counting only the distinct ones).

The product of its digits is 1000, while the sum is 24.

The square root of 21154551 is about 4599.4076792561. The cubic root of 21154551 is about 276.5675806849.

Adding to 21154551 its reverse (15545112), we get a palindrome (36699663).

It can be divided in two parts, 2115 and 4551, that added together give a palindrome (6666).

The spelling of 21154551 in words is "twenty-one million, one hundred fifty-four thousand, five hundred fifty-one".