21151251 has 12 divisors (see below), whose sum is σ = 33329400. Its totient is φ = 12818880.

The previous prime is 21151241. The next prime is 21151253. The reversal of 21151251 is 15215112.

21151251 = 970² + 971² + ... + 991².

It is not a de Polignac number, because 21151251 - 2⁵ = 21151219 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21151253) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 106726 + ... + 106923.

It is an arithmetic number, because the mean of its divisors is an integer number (2777450).

Almost surely, 2^21151251 is an apocalyptic number.

21151251 is a deficient number, since it is larger than the sum of its proper divisors (12178149).

21151251 is a wasteful number, since it uses less digits than its factorization.

21151251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213666 (or 213663 counting only the distinct ones).

The product of its digits is 100, while the sum is 18.

The square root of 21151251 is about 4599.0489234188. The cubic root of 21151251 is about 276.5531989020.

Adding to 21151251 its reverse (15215112), we get a palindrome (36366363).

The spelling of 21151251 in words is "twenty-one million, one hundred fifty-one thousand, two hundred fifty-one".