21622251 has 16 divisors (see below), whose sum is σ = 33571584. Its totient is φ = 12121824.

The previous prime is 21622241. The next prime is 21622259. The reversal of 21622251 is 15222612.

It is a happy number.

It is not a de Polignac number, because 21622251 - 2⁵ = 21622219 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21622259) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8601 + ... + 10826.

It is an arithmetic number, because the mean of its divisors is an integer number (2098224).

Almost surely, 2^21622251 is an apocalyptic number.

21622251 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21622251 is a deficient number, since it is larger than the sum of its proper divisors (11949333).

21622251 is a wasteful number, since it uses less digits than its factorization.

21622251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19490.

The product of its digits is 480, while the sum is 21.

The square root of 21622251 is about 4649.9732257294. The cubic root of 21622251 is about 278.5909268216.

Adding to 21622251 its reverse (15222612), we get a palindrome (36844863).

The spelling of 21622251 in words is "twenty-one million, six hundred twenty-two thousand, two hundred fifty-one".