21980551 has 4 divisors (see below), whose sum is σ = 22516704. Its totient is φ = 21444400.

The previous prime is 21980513. The next prime is 21980561. The reversal of 21980551 is 15508912.

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 21980551 - 2⁷ = 21980423 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 (21980561) 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, 268015 + ... + 268096.

It is an arithmetic number, because the mean of its divisors is an integer number (5629176).

Almost surely, 2^21980551 is an apocalyptic number.

21980551 is a deficient number, since it is larger than the sum of its proper divisors (536153).

21980551 is an equidigital number, since it uses as much as digits as its factorization.

21980551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 536152.

The product of its (nonzero) digits is 3600, while the sum is 31.

The square root of 21980551 is about 4688.3420310383. The cubic root of 21980551 is about 280.1213377170.

The spelling of 21980551 in words is "twenty-one million, nine hundred eighty thousand, five hundred fifty-one".