21651245 has 16 divisors (see below), whose sum is σ = 32393088. Its totient is φ = 13496640.

The previous prime is 21651221. The next prime is 21651271. The reversal of 21651245 is 54215612.

It is not a de Polignac number, because 21651245 - 2⁶ = 21651181 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27734 + ... + 28503.

It is an arithmetic number, because the mean of its divisors is an integer number (2024568).

Almost surely, 2^21651245 is an apocalyptic number.

It is an amenable number.

21651245 is a deficient number, since it is larger than the sum of its proper divisors (10741843).

21651245 is a wasteful number, since it uses less digits than its factorization.

21651245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56260.

The product of its digits is 2400, while the sum is 26.

The square root of 21651245 is about 4653.0898336482. The cubic root of 21651245 is about 278.7153951693.

Adding to 21651245 its reverse (54215612), we get a palindrome (75866857).

The spelling of 21651245 in words is "twenty-one million, six hundred fifty-one thousand, two hundred forty-five".